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Condensation of R134a in a Rectangular Microchannel to Visualize Flow Regimes at Low Mass Fluxes
Advisor: Dr. Brian M. Fronk
Submitted By: Nouman Ali
Mechanical, Industrial and Manufacturing Engineering Department
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Contents 1 Introduction ............................................................................................................................ 4
2 Literature review ..................................................................................................................... 5
3 Experimental facility ............................................................................................................... 6
4 Experimental test matrix ........................................................................................................ 7
5 Calculation .............................................................................................................................. 8
5.1 Heat transfer model ......................................................................................................... 8
5.2 Two phase flow model ..................................................................................................... 9
6 Result and discussions ............................................................................................................ 9
6.1 Flow Regimes at Saturation Temperature 40⁰C ............................................................... 9
6.1.1 Barnea Two Phase Flow Regime ............................................................................... 9
6.1.2 Breber Two Phase Flow Regime ............................................................................. 10
6.2 Flow Regimes at Saturation Temperature 55⁰C ............................................................. 11
6.2.1 Barnea Two Phase Flow Regime ............................................................................. 11
6.2.2 Breber Two Phase Flow Regime ............................................................................. 12
7 Conclusions ........................................................................................................................... 13
8 Future Work .......................................................................................................................... 13
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Acknowledgement
I would like to thank Dr. Brian Fronk, who gave us a great opportunity to do research work. Besides this we would like to acknowledge Dr. Majid Ali for full support and motivation in research skills, Tabeel Jacob for giving his precious time to us in learning about two phase flow experimental facility. The credit also goes to Michael VanderPutten and TEST Lab Fellows for their support.
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Condensation of R134a in a rectangular microchannel to visualize
flow regimes at low mass fluxes Maria Sattar, Nouman Ali
School of Mechanical, Industrial and Manufacturing Engineering (MIME) Oregon State University
Email id: [email protected], [email protected]
Abstract In this research paper, the energy efficiency concerns of refrigeration and air conditioning industry are studied. The paper presents the condensation of R134a inside horizontal rectangular microchannels to analyze the different flow regimes and vapor quality at low mass flux. The experiments were performed at different mass flux of R134a ranges between 75-150kg/m²-s at saturation temperature of 40°C and 55°C. Different regimes such as bubbly flow, intermittent flow, annular and mist annular flow were observed. The experimental data was compared against the two phase flow map of Barnea and Breber which shows good agreement for condensation of R134a. The results emphasis the cumulative effect of gravitational and surface tension forces for the transition of flow regimes from annular to intermittent flow regimes during condensation of R134a. Nomenclature
�̇�𝒘 Heat transfer rate of water Tin Inlet temperature Tout Outlet temperature Tamb Ambient temperature Cp Specific heat at constant pressure hin Enthalpy at inlet hout Enthalpy at outlet hl Enthalpy of liquid hv Enthalpy of vapor ∆𝑻𝑳𝑴 Log mean temperature difference �̇� Mass flow rate U Overall heat loss co-efficient Ac Cross-sectional area of flow channel 𝝆𝒍 Density of liquid 𝝆𝒗 Density of vapor 𝝁𝒗 Dynamic viscosity of vapor 𝝁𝒍 Dynamic viscosity of liquid DH Hydraulic diameter of microchannel Tsat Saturation temperature �̇� Volumetric flow rate �̇�𝒓𝒆𝒇 Mass flow rate of refrigerant L Total length of microchannel
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Lv Viewing length section G Mass flux of liquid and vapor Xtt Martinelli parameter Jg Dimensional gas velocity x Vapor quality
1 Introduction Energy is a necessity of society and impacts on the socio-economics of the countries. Rapid growth of industries and infrastructure increases the demand of energy. The major portion of energy is consumed in heating and cooling such as in an industry, residential buildings, and hospitals etc. The performance and efficiency of such systems depends on two building blocks: refrigerants and footprint of system. Therefore, energy used by heating and cooling can be saved through refrigerants and footprints mostly by 50% of its total energy production. By incorporating these efficient systems, energy saving can be enhanced [1]. Water and air were the initial natural refrigerants used in HVAC system in 19th century. Ammonia, methyle chloride and sulphur dioxide refrigerants that comes in first generation from 1880 to 1930s. According to their physical properties, these refrigerants had issues mainly of toxicity and flammability due to which they are neglected. The second generation started from 1931 to 1990s, which includes chlorofluorocarbon, R-11 and R-12 that have properties of non-flammability, non-toxicity and durability. These can easily be compressed in the liquid form. Due to ultra violet radiations, it becomes unstable and loses its bonding due to breakage of structure [2]. With the passage of time, the refrigerants of second generations was also replaced by hydro-fluorocarbon and hydro-chlorofluorocarbon of third generation started from 1990-2010s. These refrigerants offered same advantageous properties but have high impact on global warming potential. Fourth generation starts from 2010 to onward, which is under consideration to introduce new refrigerants. R22 have lower global warming potential and ozone depletion region. R-22 refrigerant is going to phase out due to its environmental imapcts. Till now, R134a refrigerant has been chosen and considered as a leading replacement for ammonia, CFC and HCFC in refrigeration, air conditioning cycles, heat exchangers and heat pumps for heating and cooling purposes due to its low global warming potential and zero ozone depletion region [3].
Figure 1: Different generation of refrigerants [3]
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Microchannel heat exchangers is a promising technology to increase the system’s operational efficiency of HVAC&R equipment as well as to reduce the carbon footprint of refrigeration and air conditioning unit on the global environment. The system efficiency mainly depends on design consideration for fully developed flow as well as on material aspect of flow section. In microchannel heat exchanger, effective condensation can be accomplished by enhancing effective surface area to volume ratio and, also by optimizing the saturated vapor and liquid ratio inside the channel flow section. The heat transfer in the microchannel is mainly depended on hydraulic diameter (DH), which is DH < 1mm for effective condensation inside microchannel. The motivation of microchannel phase change research has been the necessity for high-heat flux removal especially from electronic devices [4]. In this research paper, Refrigerant R134a is used inside horizontal rectangular microchannels at saturation temperature of 40°C, 55°C and saturation pressure of 147psi, 217psi over lower mass flux of 75-150 kg/m²-s to visualize the different flow regimes and also to compare experimental data points with the Barnea and Breber flow maps.
2 Literature review Understanding of flow patterns inside the horizontal microchannel can be developed by analyzing the flow regime maps. Flow regime maps are generated by considering the fluid flows and channel parameters with thermo-physical properties of condensation fluid. Researchers discussed the interrelation among mass fluxes, channel size, channel geometry, fluid properties and directing forces i.e. gravitational forces, viscous drag forces, inertial forces, buoyancy forces, and surface tension forces during the flow inside the microchannel. Suo & [5] developed the first understanding of flow regime map inside the capillary sized flow channel during adiabatic heat transfer. Their findings stated that usually in small diameter tubes, flow transition will occur in two stages: first, slug flow to bubbly flow, and secondly bubbly slug flow to annular flow at higher flow rates in zero gravity field. In this study, they considered the surface tension forces, viscous drag forces, and inertial forces as main governing forces of flow regime transition. Taitel and Dukler [6] presented a theoretical flow regime map based on dimensionless flow parameters. They formulated five flow regime transition groups included as stratified-annular, stratified-intermittent, intermittent-dispersed bubble, stratified smooth-stratified wavy, and annular dispersed liquid-intermittent-dispersed bubble. Their parametric study considered five different dimensionless parameters. They stated that at low flow rates intermittent flow can only occur when the ratio between liquid level and channel size is 0.5. They suggested that intermittent flow can only be established in the horizontal channel if the liquid level inside the channel goes higher than the center of flow sphere. Primarily the wave stability controlled the transition of flow regime. For stabilized waves, the intermittent flow will occur while higher flow rates cause instability that will lead to annular flow regimes. Generalized flow regime map was established between Martinelli parameter X and K (dimensionless parameter), where K can be obtained by multiplying the modified Froude number with the square root of Reynolds number for liquid. Breber et al. [7] developed the first condensation flow regime map. They correlated the ratio of shear forces to gravitational forces on the condensate film and the liquid volume fraction inside
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the microchannel for the flow regime map. They deduced that theoretical and experimental studies are satisfied each other for the establishment of transition boundaries in flow regime map. Their study was related with vertical and horizontal condensation of refrigerants, R-11, R-12, R-113, n-pentane and steam. They established a simplified flow regime map that satisfied the Taitel & Dukler’s theoretically flow regime map for horizontal channel condensation. Barnea et al. [8] studied the effect of surface tension forces for slug formation in small tube channels for the transition of annular to slug flow. They proposed an experimental modification to the Taitel and Dukler’s theoretical-empirical model to account for a balance between surface tension and gravitational forces in the annular to slug transition. They recommended that at low liquid flow rates in small channels (DH > 5mm), the transition from annular to slug flow can be demonstrated by studying the effect of gravitational and shear/surface tension forces during two-phase flow inside the microchannel. Recent studies regarding two-phase flow in microchannels (Dh<<1 mm) were focused on flow regime maps in terms of superficial liquid-vapor velocities for adiabatic air-water mixtures [9]. Serizawa et al. [10] investigated flow patterns during the two-phase flow of air-water mixtures flowing inside circular tubes with DH 25-100 μm. Their flow visualization was done by using the NIKON SMZ-U type microscope together with a high-speed video camera for flow visualization and observed frequent flow patterns such as; dispersed bubbly, liquid ring, annular, wispy annular, and liquid-droplet.
3 Experimental facility The experimental test facility of two phase flow is as shown in Figure 1. The test facility consisted of three loops: refrigerant loop, water loop and chiller loop [11]. Before filling the refrigerant R134a in the refrigerant loop, vacuum was created by using vacuum pump. After creating vacuum, refrigerant loop was filled with R134a. The refrigerant loop was pressurized by nitrogen gas via accumulator. The flow rate in the refrigerant loop was measured by Coriolis mass flow meter. Thermocouples of T-type were used to measure temperature between -200 to 200°C at the inlet and outlet of condenser. The pressure was measured via two pressure transducers in the referigerant loop. One pressure transducer was installed at the inlet of the pre-condenser (exit of the heater) and the other one used at the post-condenser. LabVIEW software was used to collect the experimental data. The condenser was made of stainless steel and fabricated with microchannel. The length of each channel was 200mm, height 2mm and width 25.5mm. The hydraulic diameter of rectangular microchannel was DH=0.84mm [11]. The condenser was insulated from the outside with wool and aluminum sheet to minimize the exposure of heat loss to the surrounding environment. The condenser was installed in refrigerant loop with other components through copper tubes having a diameter 1/8mm. The second loop was the water loop which consisted of water system circulating around the condenser in a counter flow wise arrangement to remove heat from refrigerant loop. Two micro syringes were used which behave as a pump. These two water pumps worked alternatively such as one sucks the water and the other one delivers water to pre-condenser from the tank filled with deionized water [11]. The third loop was the chiller loop which consist of chiller filled with an equal concentration of ethylene and glycol to cool down the refrigerant R134a in the double copper tube heat exchanger
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at the post condenser. At the same time, it was also used to cool down the water before it enter into the condenser. Chiller temperature was maintained at desired value to cool down the water and R134a.
Figure 2: Schematic representation of R134a Experimental facility[11]
Two-phase flow condensation of R134a experimentation was conducted over a range of mass flux from 75 to 150kg/m²-s and cooling water flow rate variation used from 10 to 25ml/min. Each data point was recorded for the period of four minutes under stabilized condition. The high-speed camera was installed to visualize the different flow regimes inside microchannel.
4 Experimental test matrix The following table as shown in Table 1, contains microchannel geometry dimensions and operating parameters at different observing conditions.
Table 1: Test matrix for R134a condensation study
Two Phase Study Parameters Symbol Ranges
Operating parameters
Mass flux G 75-150 Kg/m2-s Saturation temperature Tsat 40 ⁰C, 55 ⁰C Coolant volumetric flow rate V̇ 9-25 ml/min Saturation pressure Psat 147.4 psi, 217.55 psi
Microchannel geometry dimensions
Cross section area Ac Rectangular Hydraulic diameter DH 0.84 mm Length of channel L 200mm
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Viewing length Lw 90mm
5 Calculation 5.1 Heat transfer model The data acquired from the experimental facility was processed by using following governing heat transfer equations. The heat transferred in the test section is calculated from an energy balance on the water flowing in the coolant section. The heat absorbed by water from refrigerant as shown in Equation 1. �̇�𝒘 = �̇�𝒘 × 𝑪𝒑 × (𝑻𝒐𝒖𝒕 − 𝑻𝒊𝒏) (1)
The heat transfer by refrigerant in term of enthalpies is given by Equation 2.
�̇�𝒓𝒆𝒇 = �̇�𝒓𝒆𝒇 × (𝒉𝒐𝒖𝒕 − 𝒉𝒊𝒏) (2) ∆𝑇𝑖𝑛 and ∆𝑇𝑜𝑢𝑡 in Equation 3 and 4 are expressed in term of the inlet and outlet temperatures and the ambient temperature. ∆𝑻𝒊𝒏 = 𝑻𝒊𝒏 − 𝑻𝒂𝒎𝒃 (3)
∆𝑻𝒐𝒖𝒕 = 𝑻𝒐𝒖𝒕 − 𝑻𝒂𝒎𝒃 (4)
∆𝑇𝐿𝑀 is a log mean temperature difference calculated from Equation 3 and 4. ∆𝑻𝑳𝑴 =
∆𝑻𝒊𝒏−∆𝑻𝒐𝒖𝒕
𝒍𝒏(∆𝑻𝒊𝒏
∆𝑻𝒐𝒖𝒕)
(5)
The vapor quality at the inlet of the test section of the refrigerant R134a in Equation 7. It is determined by using the enthalpies. hin, is obtained from the enthalpy at the inlet of the pre-condenser, the water heat transfer rate and the refrigerant mass flow rate as shown in Equation 8. Similarly, 𝑥𝑜𝑢𝑡 is the quality at outlet of microchannel determined by same way as quality at inlet of condenser except that enthalpy at the post-condenser found by heat loss [12].
𝒙𝒊𝒏 =𝒉𝒊𝒏−𝒉𝒍
𝒉𝒗−𝒉𝒍 (6)
𝒉𝒊𝒏,𝒕𝒆𝒔𝒕 = 𝒉𝒊𝒏,𝒑𝒓𝒆 − |�̇�𝒘
�̇�𝒓𝒆𝒇| (7)
Where mass flux G is obtained by dividing mass flow rate of refrigerant to cross sectional area of channel as shown in Equation 9.
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𝑮 =�̇�𝐫𝐞𝐟
𝑨𝒄 (8)
5.2 Two phase flow model Martinelli parameter is a dimensionless number. Which is used to determine the volume fraction of liquid to vapors of flowing fluid in condensation two phase flow of microchannels. It varies with the tube size and hydraulic diameter of channel. Whereas, Jg is also a dimensionless gas velocity, which describes ratio of velocity of gas to velocity of liquid in two phase flow [13].
𝑿 = (𝝆𝒗
𝝆𝒍)
𝟎.𝟓× (
𝝁𝒗
𝝁𝒍)
𝟎.𝟏× (
𝟏−𝒙
𝒙)
𝟎.𝟗 (9)
𝑱𝒈 =𝑮×𝒙
𝝆𝒈 (10)
6 Result and discussions 6.1 Flow Regimes at Saturation Temperature 40⁰C The development of flow regimes during the condensation of R134a was also studied at saturation temperature 40⁰C. The experimental results at the saturation temperature of 40⁰C are presented in Table 2.
Table 2: Experimental results for flow visualization at 40°C saturation temperature
Mass Flux G
(Kg/m2s)
T-Sat (⁰C)
Quality x
Coolant flow rate (ml/min)
Martinelli
Parameter Xtt
Superficial Vapor
Velocity Jg*
High Speed Camera flow visualization
75 40 0.42 14 1.506 0.307
100 40 0.53 14 0.80 0.6199
150 40 0.70 14 0.299 1.515 6.1.1 Barnea Two Phase Flow Regime The results acquired are compared with the flow regime map proposed by Barnea et al. Barnea et al concluded that at low flow rates in small channels, there will be a transition from annular to slug flow. Surface tension forces were the governing forces for transition of annular flow to slug flow in small diameter tubes at low flow rates of liquid and gas. Their study was focused on air-water mixture flowing inside small tubes of hydraulic diameters 4 to 12 mm. Flow visualization indicated that the flow was in the transition region. The results of the present study were compared with the flow regime map of Barnea et al between mass flux and quality. A good comparison study was seen by our data points onto the flow map of Barnea et al. at the saturation temperature of 40⁰C against mass fluxes of 75kg/m²s, 100kg/m²s, 150kg/m²s. All data points showed good satisfaction with the flow map of Barnea et al. Intermittent flow regimes were observed at low mass flux of
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75kg/m²s, slug flow regime at 100kg/m²s and at mass flux of 150kg/m²s, there was a transition behavior seen from annular to intermittent as shown in Figure 3.
Figure 3: Comparison to Barnea et al. flow map for R134a at 40°C in 0.84mm channel
6.1.2 Breber Two Phase Flow Regime A flow map given by Breber et al. for condensation of refrigerant inside microchannels using widely data of dimensionless gas velocity against Martinelli Parameter and the data points were plotted on the flow map of Breber et al. and compared with results at different mass fluxes and found that at lower mass fluxes of 75kg/m²-s and100kg/m²-s, the flow regime lies within the intermittent region but with the increase of mass flux values at given temperatures of 40°C, the transition behavior seen from annular or mist annular to intermittent (slug, plug) flow region such as in case of 150kg/m²-s [13]. The transition from annular and mist annular to intermittent or wavy flow delayed due to the increased reduce pressure at lower qualities and these transitions exist at higher qualities depends upon the given diameter of channel. With the increase in vapor density, the liquid-vapor density ratio reduces by increasing pressure. The maximum portion of quality ranges lies within those regions where gravitation forces are more significant than vapor tension force. By comparing the experimental data with the Breber et al. flow map shows better agreement.
1
10
100
1000
10000
0.001 0.201 0.401 0.601 0.801
Mas
s Flu
x G
(kg/
m²s
)
Quality x
Intermittent Regime
Annular Regime
Stratified Regime
T-40⁰C,G-75kg/m²-s
T-40⁰C, G-100kg/m²-s
T-40⁰C,G-150kg/m²-s
Dispersed Flow
Annular Flow
Intermittent Flow Stratified Smooth & Wavy Flow
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Figure 3: Comparison to Breber et al. flow map for R134a at 40°C in 0.84mm channel
6.2 Flow Regimes at Saturation Temperature 55⁰C The experiments were conducted at low mass fluxes of refrigerant and low volumetric flow rate of coolant at the saturation temperature of 55⁰C. The experimental results at the saturation temperature of 55⁰C are presented in Table 3. It can be seen from Table 3 that the transformation of superheated vapor into liquid was reduced as the mass flux was increasing while keeping the coolant flow rate at 10 ml/min. At low mass flux, mixed vapor streams were observed.
Table 3: Experimental results for flow visualization at 55°C saturation temperature
6.2.1 Barnea Two Phase Flow Regime Figure 4 clearly depicted that the increasing coolant flow rate at a mass flux of 150 Kg/m2s resulted in the transition of flow from annular to intermittent flow region. While at low mass fluxes, the flow observed and calculated is within the intermittent region. As the coolant flow rate increased, it decreased the quality of vapors and indicated that flow transition from annular to intermittent
0.01
0.1
1
10
100
0.01 0.1 1 10 100Dim
ensi
onle
ss S
uper
faci
al v
apor
Vel
ocity
Jg
*
Martinille Parameter X
Zone 1
Zone 2
Zone 3
Zone 4
T-40⁰C, G-75 kg/m²-s
T-40⁰C, G-100 kg/m²-s
T-40⁰C, G-150 kg/m²-s
Zone 1Annular & Mist
Zone 4Bubble Present
Zone 2Wavy & stratified
Zone 3
Transition
Mass Flux G
(Kg/m2s)
Coolant flow rate (ml/min)
T-Sat (⁰C)
Quality x
Martinelli
Parameter X
Superficial Vapor
Velocity Jg*
High Speed Camera flow visualization
75 10 55 0.27 4.5 0.09 100 10 55 0.5 1.22 0.38
150 10 55 0.64 0.55 0.64
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flow at higher mass fluxes. At low velocities of fluid, laminar flow dominated because turbulence was generated against the high velocity of fluids during flow. It should be noticed that in the present study microchannels are of hydraulic diameter DH 0.84mm, while Barnea studied the flow regimes in the channel with hydraulic diameter DH 4-12mm. With the reduction of channel size, the surface tension forces are dominating at the gravitational forces. It can say that flow regime are not only affected by channel size. Mass fluxes and coolant flow rate are also vital entities in the development of flow regimes. The development of flow regimes at low mass fluxes will also be under the gravity effects.
Figure 4: Comparison to Barnea et al. flow map for R134a at 55°C in 0.84mm channel
6.2.2 Breber Two Phase Flow Regime Breber et al. proposed the first experimentally proved condensation flow regime map that was fully satisfied with the theoretically derived flow regime map of Taital and Dukler for condensation heat transfer. They stated from their study that dimensionless flow regime parameters, i.e. Superficial vapor velocity and Martinelli parameter, are good for describing adiabatic two-phase flow. So, the present study was compared with the Breber et al. flow regime map. It was resolute that at a low mass flux of about 75 Kg/m2-s the two-phase flow was in the transition region from annular to intermittent. As the flow rate increased, flow regimes shifted to the transition zone between annular to the intermittent region. At higher mass flux of about 150 Kg/m2s, it was also observed that there was a transition in flow regimes from annular flow to intermittent flow. It means that when
1
10
100
1000
10000
0.001 0.201 0.401 0.601 0.801
Mas
s Flu
x G
(kg/
m²s
)
Quality x
Intermittent Regime
Annular Regime
Stratified Regime
T-55⁰C,G-75Kg/m²-s
T-55⁰C, G-100Kg/m²-s
T-55⁰C, G-150Kg/m²-s
Dispersed Flow
Annular Flow
Intermittent Flow Stratified Smooth & Wavy Flow
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increasing the coolant flow rate, the dominance of shear forces over gravitational forces will result in the development of annular regimes. The illustrations are given in Figure 5.
Figure 5: Comparison to Breber et al. flow map for R134a at 55°C in 0.84mm channel
7 Conclusions Two phase flow condensation was studied in a horizontal smooth micro channels at lower R134a mass flux of 75-150kg/m²-s at working saturation temperatures of 40°C and 55°C and saturation pressures of 147psi and 216psi with cooling flow rates from 10-35ml/min. The experimental test results were compared with the Barnea et al. and Breber et al. paper by plotting the data points onto the flow maps of Barnea et al. and Breber et al. flow maps. It was concluded that at lower mass fluxes, intermittent flow regime is obtained but when mass flux increases, and it also shows transition from annular and mist-annular flow to intermittent flow. The experimental data points agreed well with the results of Barnea et al. and Breber et al. flow regime map.
8 Future Work To understand the surface tension and gravitational force on refrigerant flow, collection of data on vertical microchannel is required to visualize the different flow regimes and to compare the results with the flow map with other authors. Pressure drop in microchannels and void fraction is also suggested for future work on the vertical microchannel experiment.
0.01
0.1
1
10
100
0.01 0.1 1 10 100
Dim
ensi
onle
ss S
uper
faci
al v
apor
Vel
ocity
Jg
*
Martinille Parameter X
Zone 1
Zone 2
Zone 3
Zone 4
T-55⁰C, G-150 kg/m²-s
T-55⁰C, G-75 kg/m²-s
T-55⁰C, G-75kg/m²-s
Zone 1Annular & Mist Annular
Zone 4Bubble present for
condensation athigh reduced pressure
Zone 2Wavy & stratified
Zone 3
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References [1] World Economic Forum, “Energy for economic growth: Energy vision update 2012,” p.
46, 2012. [2] M. Mohanraj, S. Jayaraj, and C. Muraleedharan, “Environment friendly alternatives to
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[3] J. M. Calm, “The next generation of refrigerants - Historical review, considerations, and outlook,” Int. J. Refrig., vol. 31, no. 7, pp. 1123–1133, 2008.
[4] R. Ali, “P h a s e C h a n g e P h e n o m e n a D u r - i n g F l u i d F l ow i n M i c r o c h a n - n e l s.”
[5] P. Griffith, “C **,” 1963. [6] Y. Taitel and a E. Dukler, “A Model for Predicting Flow Regime Horizon ta I and Near -
0 - 0 I ransitions Horizontal Gas-liquid Flow,” AIChE J., vol. 22, no. 1, pp. 47–55, 1976. [7] G. Breber, J. W. Palen, and J. Taborek, “Prediction of Horizontal Tubeside Condensation
of Pure Components Using Flow Regime Criteria,” J. Heat Transfer, vol. 102, no. 3, p. 471, 1980.
[8] D. Barnea, Y. Luninski, and Y. Taitel, “Flow pattern in horizontal and vertical two phase flow in small diameter pipes,” Can. J. Chem. Eng., vol. 61, no. 5, pp. 617–620, Oct. 1983.
[9] J. R. Thome, “Mini- and Microchannel Condensation,” 2015, pp. 231–284. [10] A. Serizawa, Z. Feng, and Z. Kawara, “Two-phase flow in microchannels,” Exp. Therm.
Fluid Sci., vol. 26, no. 6–7, pp. 703–714, 2002. [11] M. VanderPutten, “Evaluation of the Predictive Capability of Two phase flow maps for
microchannel condensation of R134a at low mass flux,” Oregon State University, 2017. [12] R. Suliman, L. Liebenberg, and J. P. Meyer, “Improved flow pattern map for accurate
prediction of the heat transfer coefficients during condensation of R-134a in smooth horizontal tubes and within the low-mass flux range,” Int. J. Heat Mass Transf., vol. 52, no. 25–26, pp. 5701–5711, 2009.
[13] J. A. Milkie, S. Garimella, and M. P. Macdonald, “Flow regimes and void fractions during condensation of hydrocarbons in horizontal smooth tubes,” Int. J. Heat Mass Transf., vol. 92, pp. 252–267, 2016.
[14] J. El Hajal, J. R. Thome, and A. Cavallini, “Condensation in horizontal tubes, part 1: Two-phase flow pattern map,” Int. J. Heat Mass Transf., vol. 46, no. 18, pp. 3349–3363, 2003.
“Cultural Exchange Highlights”
After my visiting to United State of America, I am so excited to learn new things. It includes educational internships, industrial tours and other visiting excursions. Our first tour went to Bonneville Hydro Power Dam Portland Oregon, where we learned how to produced power from turbines and also how to feed different generations of Salmon (Fish). That was so much learnable and pleasant tour of the January. Some other days, we went to new port coastal area of Oregon State. Where we saw Light House and felt cold breeze flowing over the waves of sea. We hanged out with other international students along with our exchange fellows, captured a lot of pictures of beautiful scenery. We went to Lincoln city for shopping and enjoyed the snow falling on our way back to OSU that was a hectic and memorable day and we made so many international friends during our coastal area tour. Portland tour to Lan Su Chinese garden was also a wonderful visit which reflects the image of historical places of Chinese. Where different people with different ideas and thoughts came to see the beautiful historic culture and art of Chinese. Which reflect the image of their culture and civilization. Downtown Portland city was also famous regarding huge and tallest building in Oregon State. We went there to discover the whole down town city and watched NBA Basketball game in Moda center with our fellows and enjoyed the team work and disciplines of player how they played in team and showed unity that was inspirational for me.
We did our one week excursion to Arizona State. Where we attended the 2 days’ workshop on Energy policies given by Dr. Clark Miller. After attended the workshop they took a group photo all of OSU Scholars with Arizona Scholars at Arizona State University. We met with our other visiting students, visited to Phoenix downtown and Tempe Arizona under hot weather that’s was different from Oregon State. But we were happy to see the hot sunshine. We went to the Grand Canyon with Andrew to see the natural mountains with Colorado River flowing in between them that was giving eye catching views. We also visited to the Sans Francisco peak that covered with snow. On the others Day at ASU, we visited to the Heard Museum Arizona and saw the old history and learned about the culture and civilization of old people. Tulip Festival was also a pleasant excursion, we saw beautiful colorful flowers that were giving so much pleasant and joys to eyes. We took tickets and enjoyed the rock climbing, bull riding, zip line and others activities that gave us good and tough experience. Visit to Evergreen Aviation and Space Museum is my best tour till now because I had a passion to go there to see the different aero planes and learned about technologies. During our visit, I saw historic aero planes of different models and the futuristic one that was creating inspiration in me. We took tickets and watched a small video in theater on air show training of USA Air Force that was wonderful and appreciable.
We celebrated the Pakistan Resolution day with Cake and other eatable things at MIME Dept. with our OSU Mechanical family and introduced to them that how Pakistan did struggled and succeed in achieving a separate home land for our future generations so, we were very happy to meet with them that can’t be expressed in words on that special day.
I will say that I have learned a lot of skills and opportunities during my short term stay at Oregon State University where these skills gives me motivation and enthusiasm to do something in life.
Training Activities
I did three field trips including Bonneville hydro power dam, Arizona State University for attending workshops and ATAMI Lab visits. The U.S. Army Corps of Engineers built and operated Bonneville Dam at the Columbia River. Upon our arrival, one of the US Engineer introduced about the power house and dam. We saw and learnt about power production from Mechanical turbines. There were twenty Turbines installed, each have a capacity of 1200MW. The power produced was for two million population of Portland Oregon. We saw how US engineers feed and reproduce the Salmon at hydro power dam that was knowledgeable tour.
The field visit of Arizona State University is to attend the workshop on Energy polices and leadership given by Dr. Clark Miller. We attended the workshop and learnt about the energy policies making that how energy policies formulated, implemented on the society and to see those factors, which effects on environment, societies and industries. We also learnt that how can we used the better source of energy and which source of energy is cheapest and environmental friendly. At the end, we were given a small project to propose best energy model for Pakistan energy crises so that we can make better use of our resources and facilities that we have in our country. On the other day, a workshop held on Professional development and curriculum activity to ensure how to make the Curriculum vitae better for the interview during any job in industry.
Another field trip include ATAMI (Advance technology and manufacturing institute) lab, where I met with the Dr. Heilei and he introduced about the working of Nano-technologies and their manufacturing assembly. How things works at Nano scale at particular environment. We got familiar with the Hybrid Power cooling system, development in semiconductor devices, manufacturing of 3D printers and micro scale heat exchanger. ATAMI also has the widely scope to accommodate broader, deeper pockets of research excellence for Industries, OSU Research students and other colleges.
Toastmaster classes which were special arranged for us by Dr. Brian. In which I improved my English speaking skills and we were given a chance to speak in front of audience so that we can speak with confidence and without any hesitation because these skills are necessary for leadership capabilities. Upon completion of Toastmaster classes we were given a certificate of Toastmaster public speaking course that was a reward of great learning.
Training Activities
I did three field trips including Bonneville hydro power dam, Arizona State University for attending workshops and ATAMI Lab visits. The U.S. Army Corps of Engineers built and operated Bonneville Dam at the Columbia River. Upon our arrival, one of the US Engineer introduced about the power house and dam. We saw and learnt about power production from Mechanical turbines. There were twenty Turbines installed, each have a capacity of 1200MW. The power produced was for two million population of Portland Oregon. We saw how US engineers feed and reproduce the Salmon at hydro power dam that was knowledgeable tour.
The field visit of Arizona State University is to attend the workshop on Energy polices and leadership given by Dr. Clark Miller. We attended the workshop and learnt about the energy policies making that how energy policies formulated, implemented on the society and to see those factors, which effects on environment, societies and industries. We also learnt that how can we used the better source of energy and which source of energy is cheapest and environmental friendly. At the end, we were given a small project to propose best energy model for Pakistan energy crises so that we can make better use of our resources and facilities that we have in our country. On the other day, a workshop held on Professional development and curriculum activity to ensure how to make the Curriculum vitae better for the interview during any job in industry.
Another field trip include ATAMI (Advance technology and manufacturing institute) lab, where I met with the Dr. Heilei and he introduced about the working of Nano-technologies and their manufacturing assembly. How things works at Nano scale at particular environment. We got familiar with the Hybrid Power cooling system, development in semiconductor devices, manufacturing of 3D printers and micro scale heat exchanger. ATAMI also has the widely scope to accommodate broader, deeper pockets of research excellence for Industries, OSU Research students and other colleges.
Toastmaster classes which were special arranged for us by Dr. Brian. In which I improved my English speaking skills and we were given a chance to speak in front of audience so that we can speak with confidence and without any hesitation because these skills are necessary for leadership capabilities. Upon completion of Toastmaster classes we were given a certificate of Toastmaster public speaking course that was a reward of great learning.
“Cultural Exchange Highlights”
After my visiting to United State of America, I am so excited to learn new things. It includes educational internships, industrial tours and other visiting excursions. Our first tour went to Bonneville Hydro Power Dam Portland Oregon, where we learned how to produced power from turbines and also how to feed different generations of Salmon (Fish). That was so much learnable and pleasant tour of the January. Some other days, we went to new port coastal area of Oregon State. Where we saw Light House and felt cold breeze flowing over the waves of sea. We hanged out with other international students along with our exchange fellows, captured a lot of pictures of beautiful scenery. We went to Lincoln city for shopping and enjoyed the snow falling on our way back to OSU that was a hectic and memorable day and we made so many international friends during our coastal area tour. Portland tour to Lan Su Chinese garden was also a wonderful visit which reflects the image of historical places of Chinese. Where different people with different ideas and thoughts came to see the beautiful historic culture and art of Chinese. Which reflect the image of their culture and civilization. Downtown Portland city was also famous regarding huge and tallest building in Oregon State. We went there to discover the whole down town city and watched NBA Basketball game in Moda center with our fellows and enjoyed the team work and disciplines of player how they played in team and showed unity that was inspirational for me.
We did our one week excursion to Arizona State. Where we attended the 2 days’ workshop on Energy policies given by Dr. Clark Miller. After attended the workshop they took a group photo all of OSU Scholars with Arizona Scholars at Arizona State University. We met with our other visiting students, visited to Phoenix downtown and Tempe Arizona under hot weather that’s was different from Oregon State. But we were happy to see the hot sunshine. We went to the Grand Canyon with Andrew to see the natural mountains with Colorado River flowing in between them that was giving eye catching views. We also visited to the Sans Francisco peak that covered with snow. On the others Day at ASU, we visited to the Heard Museum Arizona and saw the old history and learned about the culture and civilization of old people. Tulip Festival was also a pleasant excursion, we saw beautiful colorful flowers that were giving so much pleasant and joys to eyes. We took tickets and enjoyed the rock climbing, bull riding, zip line and others activities that gave us good and tough experience. Visit to Evergreen Aviation and Space Museum is my best tour till now because I had a passion to go there to see the different aero planes and learned about technologies. During our visit, I saw historic aero planes of different models and the futuristic one that was creating inspiration in me. We took tickets and watched a small video in theater on air show training of USA Air Force that was wonderful and appreciable.
We celebrated the Pakistan Resolution day with Cake and other eatable things at MIME Dept. with our OSU Mechanical family and introduced to them that how Pakistan did struggled and succeed in achieving a separate home land for our future generations so, we were very happy to meet with them that can’t be expressed in words on that special day.
I will say that I have learned a lot of skills and opportunities during my short term stay at Oregon State University where these skills gives me motivation and enthusiasm to do something in life.
5/8/2017
1
Maria Sattar, Nouman AliAdvisor: Dr. Brian M. Fronk
Thermal Energy Systems and Transport LaboratorySchool of Mechanical, Industrial and Manufacturing Engineering
Oregon State University, Corvallis, OR, USAMay 10, 2017
Condensation of R134a in a Rectangular Microchannel to Visualize Flow Regimes at Low
Mass Fluxes
1
Contents• Introduction• Literature Review• Experiments• Flow Regimes • Comparisons• Conclusions• References
2
Residential SectorSpace & Water
Heating6%
Ventilation10%
Space Cooling11.8%
Other39%
Computers and related
components7%
Cooking2.7%
Refrigerators8%
Lighting18%
U.S. Energy Usage 2015Source: US Energy outlook 2015 3
Industrial Energy Consumption
Process & Boiler Heating
13%Facility Cooling,
Heating, and Ventilation
9%
Electochemical processes
8%
Process Cooling & Refrigeration
7%
Other processes7%Lighting
7%
Machine drives49%
U.S. Industrial Energy Usage 2013
Source: US Energy outlook 2013 4
Refrigeration & Air Conditioning Applications
5
Progression of Refrigerant in Generation
6
5/8/2017
2
Microchannel• Hydraulic Diameter <1mm• High-Heat Flux Removal
7
Two Phase Flow
Bubbly Flow
Slug Flow
Stratified Flow
Stratified Way Flow
Annular Flow
8
Literature ReviewAuthor’s
Name Phase System Channel Orientation
Cross Section
Diameter (DH) Fluids
Mass Fluxes Results
Suo & Griffith, 1964
Two PhaseFlow Adiabatic Horizontal &
Vertical Capillary 1 mm Gas-Liquid
High Mass Fluxes
Slug to annular
flow regime
Taitel & Duckler
1976
Two PhaseFlow Adiabatic Horizontal Circular 1-50 cm Air-Water
mixture
Low to high flow rates of
refrigerant
Theoretical flow
regime map
Breber et al. 1980
Two Phase Flow Adiabatic Horizontal &
Vertical Circular 8-50.8mm
R-11, R12, R-
113, Steam
Low to high Flow rates of
refrigerant
Flow Regime
Map
Barnea et al. 1983
Two Phase flow Adiabatic Horizontal Circular 4-12mm Air-Water
mixture
Low flow rates of
refrigerant
Slug Flow, Flow
Regime Map
Gaurav Nema et al. 2013
Two Phase Flow Adiabatic -
Circular & non-
Circular1-4.91 R-134a
Low to high flow
rates
Flow Transition
Criteria
9
Goals and Objectives Study of R134a two phase condensation in
rectangular microchannels. Quality measurement in microchannel. Flow visualization by using high speed
camera. Determination of the flow regimes. Comparison of experimental results with two
flow maps of Barnea and Breber.
10
R134a Experimental Facility Working
Michael VanderPutten M. VanderPutten, “Evaluation of the Predictive Capability of Two phase flow maps for microchannel condensation of R134a at low mass flux”.
11
Rectangular Microchannel Geometry
Michael VanderPutten M. VanderPutten, “Evaluation of the Predictive Capability of Two phase flow maps for microchannel condensation of R134a at low mass flux”.
Number of Channels: 5 Flow arrangement: Counter flow
12
5/8/2017
3
Experimental Test Matrix
Two Phase Study Parameters Symbol Ranges
Operating Conditions
Mass flux G 75-150 kg/m2-s
Saturation temperature Tsat 40 ⁰C, 55 ⁰C
Coolant volumetric flow rate 𝑽 9-25 ml/min
Saturation pressure Psat 147.4 psi, 217.5 psi
Microchannel Geometry
Dimensions
Cross section area of channel Ac Rectangular
Hydraulic diameter DH 0.84 mm
Length of channel L 200mm
Viewing length section Lw 90mm
13
Analytical ModellingHeat Transfer Model• 𝑸𝒘 = 𝒎𝒘 × 𝑪𝒑 × 𝑻𝒐𝒖𝒕 − 𝑻𝒊𝒏
• 𝐐𝒓𝒆𝒇 = 𝒎𝒓𝒆𝒇 × 𝒉𝒐𝒖𝒕 − 𝒉𝒊𝒏
• ∆𝑻𝒊𝒏= 𝑻𝒊𝒏 − 𝑻𝒂𝒎𝒃
• ∆𝑻𝒐𝒖𝒕= 𝑻𝒐𝒖𝒕 − 𝑻𝒂𝒎𝒃
• ∆𝑻𝑳𝑴=∆𝑻𝒊𝒏−∆𝑻𝒐𝒖𝒕
𝒍𝒏∆𝑻𝒊𝒏∆𝑻𝒐𝒖𝒕
• 𝑼 = 𝑸 × 𝑨 × ∆𝑻𝑳𝑴
Log mean temperature difference
Overall heat loss co-efficient
Heat transfer rate from refrigerant to water
14
• 𝒙𝒊𝒏 =𝒉𝒊𝒏,𝒕𝒆𝒔𝒕−𝒉𝒍
𝒉𝒗−𝒉𝒍
• 𝒉𝒊𝒏,𝒕𝒆𝒔𝒕 = 𝒉𝒊𝒏,𝒑𝒓𝒆 − 𝑸𝒘
𝒎𝒓𝒆𝒇
• 𝑮 = 𝒎𝐫𝐞𝐟
𝑨𝒄
Two Phase Flow Model
• 𝑿 =𝝆𝒗
𝝆𝒍
𝟎.𝟓×
𝝁𝒗
𝝁𝒍
𝟎.𝟏×
𝟏−𝒙
𝒙
𝟎.𝟗
• 𝑱𝒈 =𝑮×𝒙
𝝆𝒈
Heat Transfer ModelVapor quality measurement
Mass flux of refrigerant
Dimensionless gas velocity
Martinelli parameter
15
Flow Regimes at Saturation Temperature 40⁰C
Mass Flux G (Kg/m2s)
Coolant flow rate (ml/min)
T-Sat (⁰C)
Quality x
Martinelli Parameter X
Superficial Vapor Velocity Jg* Flow Visualization
75 14 40 0.42 1.506 0.09
100 14 40 0.53 0.80 0.38
150 14 40 0.70 0.299 0.64
16
Flow Regimes at Saturation Temperature 40⁰C and Mass Flux 150kg/m²-s
17
Comparison of Two Phase Flow Map of Barnea with Experimental data at 40⁰C
1
10
100
1000
10000
0.001 0.201 0.401 0.601 0.801
Mas
s Fl
ux G
(kg/
m²s
)
Quality x
Intermittent Regime
Annular Regime
Stratified Regime
Present Study: T-40⁰C, G-75kg/m²-s
Present Study: T-40⁰C, G-100kg/m²-s
Present Study: T-40⁰C, G-150kg/m²-s
Dispersed Flow
Annular Flow
Intermittent Flow Stratified Smooth & Wavy Flow
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4
Comparison of Two Phase Flow Map of Breber with Experimental data at 40⁰C
0.01
0.1
1
10
100
0.01 0.1 1 10 100
Dim
ensio
nles
s Su
perf
acia
lva
por
Velo
city
Jg*
Martinille Parameter X
Zone 1
Zone 2
Zone 3
Zone 4
Present study: T-40⁰C, G-75 kg/m²-s
present study: T-40⁰C, G-100 kg/m²-s
Present Study: T-40⁰C, G-150 kg/m-s
Zone 1Annular & Mist Annular
Zone 4Bubble Present whenhigh reduced pressure
Zone 2Wavy & stratified Zone 3
Slug & Plug
Transition
19
Flow Regimes at Saturation Temperature 55⁰C
Mass Flux G (Kg/m2s)
Coolant Flow Rate (ml/min)
T-Sat (⁰C)
Quality x
Martinelli Parameter X
Superficial Vapor Velocity Jg* Flow Visualization
75 10 55 0.27 4.5 0.09
100 10 55 0.5 1.22 0.38
150 10 55 0.64 0.55 0.64
20
Flow Regimes at Saturation Temperature 55⁰C and Mass Flux 150kg/m²-s
21
Comparison of Two Phase Flow Map of Barnea with Experimental data at 55⁰C
1
10
100
1000
10000
0.001 0.101 0.201 0.301 0.401 0.501 0.601 0.701 0.801 0.901
Mas
s Fl
ux G
(kg/
m²-s
)
Quality
Intermittent regime
Annular regime
Stratified regime
Present Study: T-55⁰C, G-75Kg/m²-s
Present Study: T-55⁰C, G-100Kg/m²-s
Present Study: T-55⁰C, G-150Kg/m²-s
Dispersed Flow
Annular Flow
Intermittent Flow Stratified Smooth & Wavy
22
Comparison of Two Phase Flow Map of Breber with Experimental data at 55⁰C
0.01
0.1
1
10
100
0.01 0.1 1 10 100
Dim
ensio
nles
s Su
perf
acia
l vap
or V
eloc
ity J
g*
Martinille Parameter
Zone 1
Zone 2
Zone 3
Zone 4
"Present Study: T-55⁰C G-150 kg/m²s
"Present Study: T-55⁰C, G-75 kg/m²s"
"Present Study: T-55⁰C, G-75kg/m²s"
Zone 1Annular & Mist Annular Flow
Zone 4Bubbly Flow
Zone 2Wavy & stratified Flow
Zone 3Slug & Plug Flow
1.5
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Conclusion
• Two phase flow condensation was studied in ahorizontal smooth micro channels at lower massfluxes.
• The experimental test results were compared with theBarnea et al. and Breber et al. paper that shows goodagreement.
• At lower mass fluxes, intermittent flow regime wasobtained due to smaller diameter of channel.
• When mass flux increases, transition exist from annularand mist-annular flow to intermittent flow due to surfacetension force domination over gravitational force.
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5/8/2017
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References[1] World Economic Forum, “Energy for economic growth: Energy vision update 2012,” p. 46, 2012.[2] M. Mohanraj, S. Jayaraj, and C. Muraleedharan, “Environment friendly alternatives to halogenated refrigerants-A review,” Int. J. Greenh. Gas Control, vol. 3, no. 1, pp. 108–119, 2009.[3] J. M. Calm, “The next generation of refrigerants - Historical review, considerations, and outlook,” Int. J. Refrig., vol. 31, no. 7, pp. 1123–1133, 2008.[4] R. Ali, “Phase Change Phenomena During Fluid Flow in Microchannels.”[5] M. Suo and P. Griffith, “Two-Phase Flow in Capillary Tubes,” J. Basic Eng., vol. 86, no. 3, p. 576, 1964.[6] Y. Taitel and a E. Dukler, “A Model for Predicting Flow Regime Horizon ta I and Near - 0 - 0 I ransitions Horizontal Gas-liquid Flow,” AIChE J., vol. 22, no. 1, pp. 47–55, 1976.[7] G. Breber, J. W. Palen, and J. Taborek, “Prediction of Horizontal TubesideCondensation of Pure Components Using Flow Regime Criteria,” J. Heat Transfer, vol. 102, no. 3, p. 471, 1980.[8] D. Barnea, Y. Luninski, and Y. Taitel, “Flow pattern in horizontal and vertical two phase flow in small diameter pipes,” Can. J. Chem. Eng., vol. 61, no. 5, pp. 617–620, Oct. 1983.
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References[9] J. R. Thome, “Mini- and Microchannel Condensation,” 2015, pp. 231–284.[10] A. Serizawa, Z. Feng, and Z. Kawara, “Two-phase flow in microchannels,” Exp. Therm. Fluid Sci., vol. 26, no. 6–7, pp. 703–714, 2002.[11] J. M. Mandhane, G. A. Gregory, and K. Aziz, “A flow pattern map for gas-liquid flow in horizontal pipes,” Int. J. Multiph. Flow, vol. 1, no. 4, pp. 537–553, 1974.[12] M. VanderPutten, “Evaluation of the Predictive Capability of Two phase flow maps for microchannel condensation of R134a at low mass flux,” Oregon State University, 2017.[13] R. Suliman, L. Liebenberg, and J. P. Meyer, “Improved flow pattern map for accurate prediction of the heat transfer coefficients during condensation of R-134a in smooth horizontal tubes and within the low-mass flux range,” Int. J. Heat Mass Transf., vol. 52, no. 25–26, pp. 5701–5711, 2009.[14] J. A. Milkie, S. Garimella, and M. P. Macdonald, “Flow regimes and void fractions during condensation of hydrocarbons in horizontal smooth tubes,” Int. J. Heat Mass Transf., vol. 92, pp. 252–267, 2016.[15] J. El Hajal, J. R. Thome, and A. Cavallini, “Condensation in horizontal tubes, part 1: Two-phase flow pattern map,” Int. J. Heat Mass Transf., vol. 46, no. 18, pp. 3349–3363, 2003.
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