Research on a novel implementation of an Ericsson cycle heat pump for near ambient refrigeration applications was performed. The concept, termed a liquid-flooded Ericsson cooler, uses liquid flooding of the compressor and expander to approach isothermal compression and expansion processes. A numerical simulation of the cycle was developed and parametric studies were performed to explore the sensitivity of the cycle to changes in various system parameters such as, pressures, heat exchanger effectiveness and working fluids. The goal of the study was to assess the viability of the technology for vending machine applications. It was found that the target cooling coefficient of performance of 1.25 could be attained if the adiabatic efficiency of the compressor and expander were 85%.

An experimental test program was conducted on a novel Ericsson cycle heat pump. The concept uses liquid flooding of the compressor and expander to approach isothermal compression and expansion processes. Open drive automotive scrolls were used in the experimental system. Numerous experiments were run at various conditions using nitrogen as the refrigerant and alkyl-benzene oil as the flooding liquid. Cooling capacities of over 670W and volumetric cooling capacities of more than 110kJ/m3 were measured. Second law efficiencies of approximately 3% were achieved. Similar to other gas cycles, the cycle performance is very sensitive to the adiabatic efficiencies of the rotating equipment and the performance of the off-the-shelf equipment was not sufficient to achieve high cycle efficiency. In addition, large pressure drops occurred in the system due to the instrumentation used and the long and arduous flow paths. The scroll compressor and expander were found to perform well considering that they were not designed for the operating conditions encountered.

A novel approach to implementing a gas Ericsson cycle heat pump was developed. The concept, termed a liquid-flooded Ericsson cooler (LFEC), uses liquid flooding of the compressor and expander to approach isothermal compression and expansion processes. Analytical models of liquid-flooded compression and expansion processes were developed using ideal gas, constant specific heat, and incompressible liquid assumptions. Special considerations for use of positive displacement compressors with fixed volume ratios are detailed. The unique behavior of a liquid-flooded compressor was explored, including the discovery of an optimum liquid flooding rate that minimizes compression power. A computer model of the LFEC cycle was developed using ideal gas, incompressible liquid, and constant specific heat assumptions. The model was used for a thorough parametric study. The purpose of the study was to explore the feasibility of the concept, identify the optimum operating parameters, and to provide a basis for the design of an experimental system.

An experimental test program was conducted on a novel Ericsson cycle heat pump. The concept uses liquid flooding of the compressor and expander to approach isothermal compression and expansion processes. Open drive automotive scrolls were used in the experimental system. Numerous experiments were run at various conditions using nitrogen as the refrigerant and alkyl-benzene oil as the flooding liquid. Volumetric cooling capacities of over 110 kJ/m 3 were measured, and second law efficiencies of approximately 3% were achieved. Similar to other gas cycles, the cycle performance is very sensitive to the adiabatic efficiencies of the rotating equipment and the performance of the off-the-shelf equipment was not sufficient to achieve good cycle efficiency. In addition, large pressure drops occurred in the system due to the instrumentation used, and the long and arduous flow paths. The scroll compressor and expander were found to perform reasonably well considering that they were not designed for the operating conditions encountered.

A novel implementation of a gas Ericsson cycle heat pump is presented. The concept uses liquid flooding of the compressor and expander to approach isothermal compression and expansion processes. A thermodynamic analysis of the cycle was performed using an EES-based computer model. In the ideal case with reversible components, the coefficient of performance (COP) of the cooler approaches the Carnot COP as the liquid flooding is increased. However, in the nonideal case when the rotating machinery operates irreversibly, there is an optimal liquid flooding rate and pressure ratio that produces the best performance. As with all gas cycles, the performance of the liquid flooded Ericsson cycle cooler is very sensitive to the efficiency of the compressor and expander. Results for two cycle configurations are presented.

A closed loop two-phase thermosyphon has been modeled based on earlier experimental and numerical studies by Mukherjee and Mudawar [1, 2]. Unlike conventional thermosyphons in which the heat dissipating device is submerged in a pool of liquid coolant, the current system uses a flow boiling arrangement. The advantage is that for a given boiling surface area, the critical heat flux (CHF) can be increased. Parametric studies with respect to adiabatic section flow areas, boiler section flow area, and system height were performed. The maximum practical heat flux that is attainable is predicted, as well as other flow parameters such as mass flow rate, flow velocities and fluid quality existing the boiler. Performance enhancements relative to the original system, may be possible by introducing a divergent cross sectional area in the boiler section that increases the system mass flow rate. It can also, however, reduce the flow velocity in certain sections of the boiler, tending to reduce the boiler CHF. Experimental studies are recommended to determine if an actual improvement can be realized.