Abstract
The present work aims to perform the thermodynamic analysis of an ejector expansion refrigeration cycle (EERC) with a constant-pressure two phase flow ejector and to present the effect of primary nozzle throat diameter on cooling capacity of the EERC. The refrigerant is R134a. In order to achieve these objectives, a computational program is developed using EES software to simulate the system. Mathematical modeling of EERC and applied computational procedure are reported in detail. Operation under critical mode is favorable in ejector operation in terms of high entrainment ratio and enhanced ejector performance. As a result, in this present study, ejector of the refrigeration cycle operates under critical conditions and normal shock occurs at the end of the constant area mixing section. Not an iteration process but Henry and Fauske model is applied to determine the physical properties of the fluid under critical conditions.
Highlights
In recent years, ejectors have received much attention in stationary and mobile air-conditioning applications due to their ability in throttling loss reduction and increase of system efficiency
While most of the studies are performed for transcritical applications of high pressure fluids, i.e. carbon dioxide, later thermodynamic analyses showed that ejectors offer remarkable efficiency improvement in refrigeration systems working with low pressure refrigerants, as well
Ejectors allow the expansion process to get closer to isentropic expansion process in comparison to that of conventional vapor compression refrigeration cycle (CVCRC) and reducing the thermodynamic loss of the cycle
Summary
Ejectors have received much attention in stationary and mobile air-conditioning applications due to their ability in throttling loss reduction and increase of system efficiency. The ejector performance can be divided into three operational modes, according to the back pressure of the ejector: the critical, subcritical and back flow modes Relation of these modes with back pressure and the variation of entrainment ratio (w) is depicted in Figure 1 (based on [17]). Detailed explanation is available in [2,14,17,18] In this present study, variation of primary nozzle throat diameter with cooling capacity is analyzed for a constant pressure type ejector used in an EERC. At the exit of the condenser, the phase of the refrigerant is saturated liquid and enters the ejector at condenser pressure and temperature (state point 1, Figure 2). The refrigerant enters into the expansion valve after leaving the separator and the pressure and temperature of the saturated liquid are dropped to those of the evaporator (state point 8, Figure 2). After the evaporator (state point 2, Figure 2) the refrigerant is in saturated vapor phase and is at evaporator pressure/temperature
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