Session: K6-09: HEAT TRANSFER IN ENERGY SYSTEMS - WASTE HEAT II

Paper Number: 138693

138693 - Simulation of Liquid Piston, High Temperature Stirling Cycle Heat Pumps 

Abstract: 

       The ideal Stirling heat pump cycle consists of isothermal compression and expansion processes along with isovolumetric regeneration processes. In the regeneration processes, heat is transferred to or from the working gas and stored in a porous regenerator. The gaseous working fluid and isothermal heat addition and rejection processes provide significant advantages for high temperature heat pumps in waste heat upgrading applications. However, the isothermal heat transfer processes can be difficult to achieve in practice. One approach is the use of liquid pistons intruding into a porous fill.

        Here we detail simulations predicting power output and efficiency of a liquid piston Stirling cycle heat pump for given design and operating parameters. The system considered is an alpha configuration with separate “hot side” and “cold side” cylinders in which the working gas is compressed and expanded respectively. The model incorporates the basic thermodynamic behavior of the working gas during the component processes along with finite difference based numerical modelling of the heat transfer and viscous drag in the heat exchangers. These two losses significantly impact system performance and design considerations. Losses due to dead volume in the system are also modelled.

      Simulation outputs include the coefficient of performance and thermal power density. The system geometry, frequency, mean pressure, compression ratio, regenerator effectiveness, and porous media properties are varied, and the balance of efficiency and power density is considered. The simulation results are compared against literature and preliminary experimental results from a prototype system. Analysis suggests that liquid piston Stirling cycle heat pumps can be implemented in industrial settings for waste heat upgrading applications.

 

Presenting Author: Sebastian Edinger University of California, Merced

Presenting Author Biography: Mechanical engineering PhD candidate at the University of California, Merced with an emphasis in thermodynamics, heat transfer, and fluid mechanics. Currently research topic is high temperature heat pumps for industrial waste heat recovery. Research interests include industrial and manufacturing technology, internal combustion engines, and systems engineering.

Authors:

Sebastian Edinger University of California, Merced
James Palko University of California, Merced