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EJECTOR EXPANSION REFRIGERATION SYSTEM

S I J O K K

S1 M-TECH

M112

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CONTENTS1. Introduction2. Ejector-expansion refrigeration cycle3. Working of EERS4. Constant area ejector5. working of constant area ejector6. System analysis7. Results and discussion8. Conclusion 9. References

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INTRODUCTION•Refrigeration consumes major part of electricity

•70% systems using vapor compression

•Old and less efficient

•To overcome this difficulty high energy efficient technique should be selected

•Use of EERS improves system performance

•Decreases compressor power

•Increase COP

•Recover expansion process by isentropic expansion process

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EJECTOR-EXPANSION REFRIGERATION CYCLE

Ejector-Expansion Refrigeration Cycle with its P-h diagram

Pc

Ps

PePb

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EJECTOR-EXPANSION REFRIGERATION CYCLE(cond…)

•Main parts1) Compressor2) Condenser3) Two phase flow ejector4) Separator5) Expansion valve 6) Evaporator

•Modifications affects1. Expansion losses2. Suction pressure

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WORKING OF EERC

•Compression

•Condensation

•Motive flow to ejector

•Liquid expansion in expansion device

•Evaporation (cooling)

•Secondary flow

•Mixing of flows

•Finally reaches the separator

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CONSTANT AREA EJECTOR

Constant-area mixing ejector. a) Schematic diagram b) Pressure profile c) Velocity profile.

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CONSTANT AREA EJECTOR

•Main parts are1. Motive nozzle

2. Suction chamber

3. Suction nozzle

4. Constant area mixing section

5. Diffuser

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WORKING OF CONSTANT AREA EJECTOR

•Primary flow expansion in motive nozzle (P1b=Pb < Peva)

•Secondary flow expansion to pressure (P2b=Pb)

•Mixed together to a pressure (P3m > Pb)

•Choke wave take place

•Pressure increases and velocity reduces

•Further increase of pressure in diffuser (Psep )

•Intermediate pressure

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WORKING OF CONSTANT AREA EJECTOR

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SYSTEM ANALYSIS

•Based on conservation of mass, energy and momentum

•Major assumptions area) Neglect the pressure drops in tubes ,cooler and evaporator

b) Steady state 1D flow

c) No heat loss to environment

d) Zero velocities at the inlet of both nozzles

e) Friction losses in nozzle and diffuser defined in isentropic efficiencies

f) Liquid vapor separator is 100% efficient

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Ejector analysis•Recovers expansion losses

•Increases compressor suction pressure

•Analysis based on conservation equations of fluid particles in following sections

a. Motive nozzle

b. Suction nozzle

c. Mixing section

d. diffuser

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Motive nozzle•From P-h diagram isentropic efficiency of nozzle

•ηmn = (h1b – h1)/ (h1b, is − h1)

•Velocity at nozzle exit

•Mass flux at exit

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Motive nozzle•From conservation of mass area of motive stream at 1b

•Primary mass flow

•ω=ṁs / ṁp

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Suction nozzle•The equations are

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Constant area mixing section•From conservation of momentum Velocity after mixing calculated as

•Mass flux

•Applying conservation of energy, specific enthalpy given by

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Diffuser •Specific enthalpy at diffuser exit

•Exit isentropic specific enthalpy

ηd is the isentropic efficiency of the diffuser

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Performance characteristics of EERS•The cooling capacity is calculated as

•Compressor power

η com = (h 5is − h4 )/ (h5 – h4 )

•COP

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Performance characteristics of EERS•Pressure lift

•Ejector efficiency

hch2hb ha

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RESULTS AND DISCUSSION

•Effect of evaporation temperature ṁp ṁs Plift MF ω COP

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Effect of evaporation temperature

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Effect of condensation temperature

ṁp ṁs MF Plift ω COP

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Effect of condensation temperature

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CONCLUSION•Performance of EERS is evaluated by theoretical analysis

•COP increases with increase of evaporation temp

•Compressor work decreases with increase of evaporation temp

•COP decreases with increase of condensing temp

•Compressor increases with increase of condensing temp

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REFERENCES1. Hassanain, M., Elgendy, E., Fatouh, M., Ejector expansion refrigeration system:

ejector design and performance evaluation, International Journal of Refrigeration (2015) .

2. Li Zhao , Xingyang Yang , Shuai Deng , Hailong Li, Zhixin Yu. Performance analysis of the ejector-expansion refrigeration cycle using zeotropic mixtures International journal of refrigeration(2015)

3. Rounak Sahni ., Ejector Expansion Refrigeration Systems . International Journal of Refrigeration (2015)

4. Ersoy, H. K., Sag, N. B., 2014. Preliminary experimental results on the R134a refrigeration system using a two-phase ejector as an expander. International Journal of Refrigeration. 43, 97-110.

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REFERENCES

5. Hu, J., Shi, J., Liang, Y., Yang, Z., Chen, J., 2014. Numerical and experimental investigation on nozzle parameters for R410A ejector air conditioning system. International Journal of Refrigeration 40, 338-346.

6. Chaiwongsa, P., Wongwises, S., 2007. Effect of throat diameters of the ejector on the performance of the refrigeration cycle using a two- phase ejector as an expansion device. International Journal of Refrigeration 30, 601- 608.

7. Bilir, N., Ersoy, H., 2009. Performance improvement of the vapor compression refrigeration cycle by a two-phase constant area ejector. International Journal of Energy Research 33, 469–480.

8. Nehdi, E., Kairouani, L., Bouzaina, M., 2007. Performance analysis of the vapor compression cycle using ejector as an expander. International Journal of Energy Research 31, 364–375.