Experimental analysis of coil finned tube type Heat Exchanger for Helium Liquefaction plant

Patel Jay Mahendrakumar1, Prof. S.M Mehta2

1,2L.D. College of Engineering, Department of Mechanical Engineering, Ahmedabad-15

Refer

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• Gas liquefaction system :Very crucial part as it is used to liquefy various gases like N2 , O2 ,He, etc.., Various types of it like linde-hampson, preooled linde-hampson, linde dual pressure, cascade, Claude, kapitza, heylandt etc., Components of any liquefaction systems are compressor, Heat exchanger, expander device etc.

• Heat Exchanger: It is a heart-as it exchanging the heat between two fluids, Basically there are two types of Heat exchanger-RECUPETORS and REGENERATORS.

• TUBE FIN HET EXCHANGER: It consists- Tube of Different shape like Rectangular, Round, Elliptical , Fins are generally used on the outside, but they may be used on the inside of the tubes in some applications.

• Application: Cooler/Heater, Liquefier, Vaporiser, Isothermal reactor

Literature Survey

Problem FormulationThe coil finned tube Heat exchanger is the first type of medium capacity heat exchanger. In this dissertation the fabrication and experimental analysis of this heat exchanger will be carried out for helium liquefaction plant

Design Methodology

Introduction Literature Survey Problem Formulation Design Methodology Drawings and Specifications Certificates and images Proposed Experimental Set up References

Over view Introduction

• Design side:• Croft and Tebby : In 1970 croft and tebby presented

the expression for thermal design and they have suggested the correlations for calculation of heat transfer coefficient for shell and tube side flow. Although this paper did not throw light on any pressure drop relation

• Croft and Cosier: In the same year croft and cosier were designed a new form of finned tube heat exchanger by the method described by croft tebby.

• M.D. Atrey : In 1998 M.D. Atrey did the thermodynamic analysis of Collins helium liquefaction cycle. In his analysis he were used the two reciprocating expander with Collins helium liquefier.

• Prabhat Kumar Gupta: In 2007 Prabhat kumar gupta, P.k. Kush, Ashesh Tiwari presented the design and optimization of coil finned tube heat exchanger for cryogenics application. In their study, geometry of heat exchanger has been derived taking into consideration the clearance provided for manufacturing of the heat exchangers and an optimized geometrical configurations have been find out.

• Prabhat kumar Gupta’s second law analysis: The special focus of his analysis is the study of effect of these irreversibilities on the performance of heat exchangers through second law analysis. It is observed that the effect of ambient heat-in-leak is different for the balanced and imbalanced counter flow high NTU heat exchangers.

• Experimental Side:• Collins : The coil finned tube heat exchangers were

first used by Collins in his helium liquefier in 1947.A unique extended surface heat exchanger design involving flow in concentric tubes.

• Giest and Lashmet: In 1960 giest and lashmet were used these heat exchanger in their experiment of miniature joule Thomson refrigeration system.

• Prabhat kumar Gupta’s Experimental research on overall heat transfer coefficient : The experiments were conducted in the range of effective Reynolds number 500–1900. The effect of diametrical clearance on the prediction of overall heat transfer coefficient is also investigated experimentally.

• Prabhat kumar Gupta’s Experiments on Pressure drop : All experiments were performed at room temperature in the Reynolds number range of 3000–30,000 for tube side and 25–155 for shell side. To evaluate pressure drop within heat exchangers at room temperature, a separate test set-up was planned.

• Geometry for thermal and pressure drop design:[1]The total shell side free flow area Asc, is given by

Asc= π Dc(df + c) – πDe[(df – do)nt + do][2]Free flow area offered by the fins cross-section, Afc

Afc= π De[(df – do)(1 – nt)][3]Free flow area offered by the clearance cross-section, Acc

Acc= π Dec[4]The surface area offered by the outer finned surface in one coil; As

=-)+(1-nt)+nt][5[The perimeter of outer finned surface (surface area per unit axial length), so

=[6]The perimeter of inner tube surface (surface area per unit axial length), si

=•Design fundamentals:[7]Bypass area factor k is given by,

k = [8]So, the actual mass flow rate passing through the fins is

mf =[9]The hydraulic diameter is

Dh = [10]The Reynolds number based on the total cross-section area available for shell side flow when there is no clearance and can be calculated as follows

ReWOC = [11]The Reynolds number will be calculated based on the actual flow passes through the fins and can be given by

Ref = [12]The mass flow rate per unit free-flow area G is calculated from following Equation

G = •Thermal Design[13]The total heat duty Q of the hot fluid which has to be removed by exchanging the energy with the cold fluid is expressed as follows

Q = Ch(Th,in – Th,out)= UL ΔTLMTD[14]ΔTLMTD is the log mean temperature difference, given by

ΔTLMTD = [15] The value of heat transfer co efficient of inner and outer stream and is given by

hi = 0.033= 0.027

[16] The overall heat transfer coefficient U (W/m K) based on per unit axial length of heat exchanger can be given by

U =

[17]Now we can find the require tube length for heat transfer from equation as follow

Q = U L ΔTLMTD• Pressure Drop[18]Now the Pressure drop is calculated from following equation for both side

ΔP = • Ln2 bath Design:[a]Decide the type of boiling occurs in the LN2 Dewar From Following equation and LN2 boiling chart

∆T = Tw – Tsat [b]In my case nucleate boiling is occurs so I can calculate the out side heat transfer by Rohsenow Correlation as follow

[c]Outside Heat transfer coefficient is calculated ho from following equation

[d]Now inside heat transfer coefficient is calculated by following equation

[e]Over all heat transfer coefficient U is calculated from following Equation

[f]Heat transfer Q is given byQ = mh ch (Tin – Tout )

[g]Heat transfer area is calculated as followQ = U A

[h]Length of the tube required is calculated from following equation

Proposed Experimental set up

[1]R.K.Shah and D.P Sekulic, Heat Exchanger, University of Kentucky.:17.19-20. [2] Croft AJ, Tebby PB. The design of finned-tube cryogenic heat exchangers. Cryogenics 1970(June):236–8.

[3]Croft AJ, Cosier J. A new form of finned-tube heat exchanger. Cryogenics 1970(June):239–40.[4] Atrey MD. Thermodynamic analysis of Collins helium liquefaction cycle. Cryogenics 1998; 38: 1199–206.[5] Gupta, P.K., Kush, P.K., Tiwari, A., 2007b. Design and optimization of coil finned-tube heat exchangers for cryogenic .