Modeling and analysis of a Vuilleumier heat pump system
Date
1997
Authors
Vidyadharan, Rakesh
Major Professor
Advisor
Maldonado, G. Ivan
Committee Member
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Abstract
A traditional Vuilleumier heat pump system using helium as the working fluid and working as a summer air-conditioning system has been modeled and its capabilities explored. The performance of various heat exchanger configurations with varying frontal areas was studied. The irreversibilities introduced into ideal operation of the system due to fluid friction to helium flow through the heat exchangers has been studied. Cross flow heat exchanger configurations with the heat exchange medium (air) flowing normal to banks of finned tubes, as presented in Kays and London (1964) were adopted, and the frictional pumping power requirement for each configuration as a function of the frontal area was calculated.
In general, heat exchanger configurations possessing relatively low hydraulic diameter, high ratio of free-flow area to frontal area, and larger tube diameters were found to be optimal. For applications where heat exchanger dimensions are unconstrained, the total frictional power expenditure could be limited to less than 1% of the total cooling capacity of the system. However, for applications where the heat exchanger size is constrained, additional power ranging from 10% to 300% would need to be supplied depending upon the severity of the constraint. The effects of varying the high temperature level and the phase difference between the engine displacer and the refrigerator displacer was also studied.
The temperature of the high temperature heat addition was varied in the range 823-373K. The simulation was conducted for phase angles β between the power and cooling cycles in the range 0°≤ β ≤ 180°. The net heat input required was found to increase at a very slow rate when compared to the increase in the system's cooling capacity, and consequently the COP. The net heat transfer rate was found to increase from a value of zero for a β of 0° to a maximum for a β of 90°,and then decrease back to zero for a β of 180°.
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thesis