Performance analysis of reciprocating regenerative magnetic heat pumping
Abstract
Transient flow phenomena in the regenerator tube of reciprocating magnetic heat pumps have been studied numerically and experimentally. In the numerical study, two approaches were taken: (1) solving the energy balance equations for fluid through a porous bed directly and (2) solving the NavierStokes equations with a buoyancy force term in the momentum equation. A flow thermal mixing problem was found in both approaches because of the pistonlike motion of the regenerator tube that hinders the development of the temperature. The numerical study results show that a 45 K temperature span can be reached in 10 minutes of charge time through the use of a 7Tesla magnetic field. Using the second numerical approach, temperature stratification in the regenerator fluid column was clearly indicated through temperature rasters. The study also calculates regenerator efficiency and energy delivery rates when heating load and cooling load are applied. Piecewise variation of the regenerator tube moving speed has been used in the present numerical study to control the mass flow rate, reduce thermal mixing of the flow and thus the regenerative losses. The gadolinium's adiabatic temperature has been measured under 6.5 Tesla of magnet field and different of operating temperatures ranging from 285 K to 320 K. Three regenerative heat pumping tests have also been conducted based on the Reynolds number of the regenerator tube flow, namely Re=300, Re=450, and Re=750 without loads. Maximum temperature span are 12 & 11 K and 9 K for the case of Re=300, Re=450 and Re=750, respectively. Experimental data are in good agreement with the numerical calculation results, and have been used to calibrate the numerical results and to develop a design database for reciprocatingtype roomtemperature magnetic heat pumps.
 Publication:

NASA STI/Recon Technical Report N
 Pub Date:
 February 1994
 Bibcode:
 1994STIN...9435683C
 Keywords:

 Fluid Mechanics;
 Heat Pumps;
 Heat Transmission;
 Magnetic Pumping;
 Reciprocation;
 Thermodynamic Properties;
 Transient Heating;
 Gadolinium;
 Heating;
 Magnetic Fields;
 NavierStokes Equation;
 Regenerators;
 Temperature Distribution;
 Fluid Mechanics and Heat Transfer