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Research Papers: Geothermal Energy

Optimal Allocation of Heat Exchanger Inventory of a Two-Stage Vapor Compression Cycle for Maximum Coefficient of Performance

[+] Author and Article Information
M. J. Morales

Department of Mechanical and Aerospace Engineering, University of Florida, P.O. Box 116300, 232 MAE Building B, Gainesville, FL 32611-6300manuelj76@hotmail.com

S. A. Sherif1

Department of Mechanical and Aerospace Engineering, University of Florida, P.O. Box 116300, 232 MAE Building B, Gainesville, FL 32611-6300manuelj76@hotmail.com

1

Corresponding Author.

J. Energy Resour. Technol 130(2), 022301 (May 16, 2008) (11 pages) doi:10.1115/1.2906108 History: Received August 03, 2004; Revised January 02, 2008; Published May 16, 2008

The purpose of this study is to investigate how the heat exchanger inventory allocation plays a role in maximizing the thermal performance of a two-stage refrigeration system with two evaporators. First, the system is modeled as a Carnot refrigerator and a particular heat transfer parameter is kept constant as the heat exchanger allocation parameter is allowed to vary. The value of the heat exchanger allocation parameter corresponding to the maximum coefficient of performance (COP) is noted. The results are compared to those of a non-Carnot refrigerator with isentropic and nonisentropic compression. It is found that the Carnot refrigerator can be used to predict the value of the heat exchanger allocation parameter where the maximum COP occurs for a non-Carnot refrigerator. In order to improve the accuracy of that prediction, the predicted value of the heat exchanger allocation parameter has to be inputted into the set of equations used for the non-Carnot refrigerator. This study is useful in designing a low-cost, high-performance refrigeration system.

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Copyright © 2008 by American Society of Mechanical Engineers
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Figures

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Figure 1

Schematic diagram of a two-stage Carnot refrigerator

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Figure 2

Temperature-entropy (T-s) diagram of a two-stage Carnot refrigerator

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Figure 3

Schematic of a two-stage non-Carnot refrigerator

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Figure 4

Temperature-entropy (T-s) diagram of a two-stage non-Carnot refrigerator

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Figure 5

Log P-h diagram of a two-stage non-Carnot refrigerator

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Figure 6

COP versus x1=(UA)1∕(UA)tot for a constant cooling rate at the low-temperature evaporator in a Carnot refrigerator (x2=0.16)

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Figure 7

COP versus x1=(UA)1∕(UA)tot for a constant cooling rate at the low-temperature evaporator in a Carnot refrigerator (x2=0.25)

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Figure 8

COP versus x1=(UA)1∕(UA)tot for a constant cooling rate at the low-temperature evaporator in a Carnot refrigerator (x2=0.45)

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Figure 9

COP versus x2=(UA)2∕(UA)tot for a constant cooling rate at the low-temperature evaporator in a Carnot refrigerator (x1=0.09)

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Figure 10

COP versus x1=(UA)1∕(UA)tot for a constant cooling rate at the high-temperature evaporator in a Carnot refrigerator (x2=0.10)

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Figure 11

COP versus x1=(UA)1∕(UA)tot for a constant cooling rate at the high-temperature evaporator in a Carnot refrigerator (x2=0.18)

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Figure 12

COP versus x1=(UA)1∕(UA)tot for a constant cooling rate at the high-temperature evaporator in a Carnot refrigerator (x2=0.50)

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Figure 13

COP versus x1=(UA)1∕(UA)tot for a constant heat rejection rate in a Carnot refrigerator (x2=0.25)

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Figure 14

COP versus x1=(UA)1∕(UA)tot for a constant heat rejection rate in a Carnot refrigerator (x2=0.50)

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Figure 15

COP versus x1=(UA)1∕(UA)tot for a constant heat rejection rate in a Carnot refrigerator (x2=0.75)

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Figure 16

COP versus x1=(UA)1∕(UA)tot and x2=(UA)2∕(UA)tot for a constant cooling rate at the low-temperature evaporator in a Carnot refrigerator

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Figure 17

COP versus x1=(UA)1∕(UA)tot for a constant cooling rate of 10.00kW at the low-temperature evaporator in a non-Carnot refrigerator with isentropic compression

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Figure 18

COP versus x1=(UA)1∕(UA)tot for a constant cooling rate of 10.00kW at the high-temperature evaporator in a non-Carnot refrigerator with isentropic compression

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Figure 19

COP versus x1=(UA)1∕(UA)tot for a constant cooling rate of 10.00kW at the low-temperature evaporator in a non-Carnot refrigerator with nonisentropic compression

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Figure 20

COP versus x1=(UA)1∕(UA)tot for a constant cooling rate of 10.00kW at the high-temperature evaporator in a non-Carnot refrigerator with nonisentropic compression

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