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Ian W. Eames, Mark Worall and Shenyi Wu
An experimental investigation into the novel integration of a jet-pump
refrigeration cycle and a novel jet-spay thermal ice storage system.
University of Nottingham, Faculty of Engineering
Corresponding author: [email protected]
Sustainable Thermal Energy Management in the Process Industries International Conference (SusTEM2011)
Introduction
• Motivation behind the project.
• Description of the proposed jet-pump thermal ice storage system
• Some design details
• Experimental results
• Conclusions
• Some related research
Project motivation
• Waste heat or solar or powered air conditioning using a low capital cost chiller systems based on the jet-pump cycle.
• TIS to provide building cooling when heat supply falls or when the sun goes in.
• Improve system utilization by better balancing of cooling capacity against load.
Showing the proposed jet-pump – thermal ice storage system
Details of the experimental jet-pump
Principal dimensions of the primary nozzle
Photo of experimental machine
Comparing theoretical and experimental flow through the primary nozzle (steam data)
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
105 110 115 120 125 130 135 140
Generator saturation temperature (oC)
Pri
mary
no
zzle
mass f
low
(g
/s)
theoretical 1-D supersonic flow data
measured data
Theoretical data assumes steam to be a semi-perfect
gas (g = 1.3, Cp =Cpg = f(Tsat)) and 1-D sonic flow at
the nozzle throat. The resulting average error in this
case was calculated to be -0.7%.
Measured nozzle throat dia. = 2.02 mm
Variation in entrainment ratio with condenser pressure (steam data)
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
20 25 30 35 40 45 50
Condenser pressure (kPa)
En
train
me
nt
rati
o
Te = 2.5°C
Te = 5°C
Te = 7.5°C
Te = 10°C
Nozzle throat dia = 2 mm
Diffuser throat dia = 18 mm
Generator temperature 120 °C
Showing how entrainment ratio varies with generator and evaporator pressure (R134A data)
0.1
0.12
0.14
0.16
0.18
0.2
0.22
0.24
6.5 7 7.5 8 8.5 9 9.5
en
train
men
t ra
tio
(m
evap/m
gen)
Tevap = 8oc
Tevap = 6oC
Tevap = 4 oC
Showing how critical condenser pressure varies with generator and evaporator pressure (134A data)
2
2.2
2.4
2.6
2.8
3
3.2
3.4
3.6
6.5 7 7.5 8 8.5 9 9.5
Cri
tical
sec
on
dar
y p
ress
ure
rat
io (-
)
Showing measured entrainment ratio values as a function of evaporator steam saturation density, (steam data).
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
2 3 4 5 6 7 8 9 10
Evaporator saturated vapour density (kg/m3 x 1000)
En
train
men
t ra
tio
Generator pressure/temperature = 198.5 kPa/120oC
measured data
extrapolated
correlation
entrainment ratio
at 0oC = 0.275
Showing the variation in evaporator vapour temperature and circulation water temperature during TIS charging.
-2
0
2
4
6
8
10
12
0 10 20 30 40 50 60 70 80
Time (mins)
Evap
ora
tor
tem
pe
ratu
re (
°C)
vapour temperature
water temperature
generator temperature 120 °C
primary throat 2mm dia
average ice growth rate = 0.81 g/s
spray nozzle flow = 10 g/s
Showing the measured variation in ice production with generator temperature for 2 rates of spray-nozzle flow
0
0.2
0.4
0.6
0.8
1
1.2
1.4
110 115 120 125 130 135
Generator temperature (oC)
Ice p
rod
ucti
on
rate
(g
/s)
spray nozzle flow = 9g/s
spray nozzle flow = 10 g/s
Nozzle throat dia = 2mm, diffuser throat dia = 18 mm
Predicted flow ratio versus degrees of sub-cooling
0
0.05
0.1
0.15
0.2
0.25
0 2 4 6 8 10 12 14 16 18 20
Degrees of supercooling (DTsc) (degK)
mass r
ati
o (
m i/m
sp
ray)(
kg
/kg
)
scpipffg
scpf
pf
spray
.
i
.
TCChifh
TC1
TscC
m
m
D
D
D
mi/mspray = 0.0826
mi/mspray = 0.1244
Showing the measured ratio of spray-ice production as a function of steam flow through the primary nozzle
0
0.2
0.4
0.6
0.8
1
1.2
1.4
105 110 115 120 125 130 135 140
Generator saturation temperature (oC)
Ice r
ate
/no
zzle
flo
w (
g/g
)
spray rate = 10.1 g/s
spray rate = 9 g/s
Nozzle throat dia. = 2mm, diffuser throat dia. = 18mm mm
Some conclusions…
• With an evaporator temperature of 10oC results showed it is possible to cool with a thermal COP of about 0.5.
• A thermal COP of 0.8 has been measured by Eames et al (7) using R254fa, an organic refrigerants, at the same condenser and evaporator temperatures but with a lower generator temperature of 110oC.
• Results show that , entrainment ratio is a linear function of secondary flow density.
• An entrainment ratio of 0.275 is estimated at 0oC when the machine was making ice.
• Results suggest water droplets are first super-cooled by a flash evaporation process in their flight from the spray nozzle before freezing on impact with the ice layer at the vessel wall.
Some more conclusions…
• Water spray flow of 9 g/s gave an ice growth rate of 1.12 g/s.
With a spray flow of 10.1 g/s the average ice storage rate
reduced to 0.835 g/s.
• The average rates at which ‘cooling potential’ is stored was
calculated using the empirical flow data to be 280 W and 373 W
at 9 and 10.1 g/s spray flow respectively.
• Analysis described in the paper shows:
• A thermal coefficient of performance for the thermal ice storage
process of 0.176 was measured.
• To a first order approximation the mass of ice produce is equal to
the mass of steam that flows through the primary nozzle.
• Effect of spray nozzle flow rate needs further investigation.
2
m
m
maxgen
.
ice
.
A maximum of 7.5 kg of ice can be per kg of liquid water evaporated and entrained by the jet-pump.
Related studies: An investigation into the use of encapsulated ice for jet-pump thermal storage – Ian W. Eames and Jorge Caeiro.
Related studies: An investigation into the use of encapsulated ice for jet-pump thermal storage – Ian W. Eames and Jorge Caeiro.
Related studies: An investigation into the use of encapsulated ice for absorption cycle combined with thermal storage - Ian W. Eames and Jorge Caeiro.
Acknowledgements
The authors wish to acknowledge with grateful thanks the financial support of Sanken Setsubi Kogyo of Tokyo, Japan, for their support of the research described in this presentation.
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