Regenerator optimization for Stirling cycle refrigeration II

Conference · Fri Jul 01 04:00:00 EDT 1994

OSTI ID:10163593

Colgate, S A; Petschek, A G

A cryogenic regenerator for a Stirling cycle is discussed using fractional loss or entropy gain as the criterion of performance. The gas losses are treated separately from heat storage medium losses. We argue that the optimum design corresponds to uniform channel flow with minimum turbulence where the gas velocity and channel width are optimized as a function of gas temperature. The maximization of heat transfer from the gas to the wall and the minimization of entropy production by friction leads to a gas flow velocity equal to sound speed times loss fraction, 1/{sigma}. This velocity and an axial thermal conductivity in the gas leads to a minimum channel width and characteristic length, L=T(dz/dT). A particular scaling of width, W{sup 2} = W{sub o}{sup 2}T{sup 1/2}, and length, L = L{sub o} T{sup {minus}1/2} leads to a design where longitudinal conduction decreases as T{sup 3/2} and the remaining two losses, transverse conduction and friction are equal and constant. The loss fraction, 1/{sigma}, must be made quite small, {approximately}(1/60) in order that the cumulative losses for a large temperature ratio like 300K to 4K, be small enough, like 20% to 40%. This is because half the entropy generated as a loss must be transported first to the cold end before returning to the hot end before being rejected. The dead volume ratio then determines the minimum frequency and with it and the pressure the necessary wall properties. The thermal properties of the channel wall must then accommodate this cyclic heat flow without substantially increasing the loss fraction. This generation of entropy in the walls is derived in terms of the wall heat capacity and thermal conductivity.

• Research Organization: Los Alamos National Lab., NM (United States)
• Sponsoring Organization: USDOE, Washington, DC (United States)
• DOE Contract Number: W-7405-ENG-36
• OSTI ID: 10163593
• Report Number(s): LA-UR--94-2104; CONF-940665--1; ON: DE94014477
• Country of Publication: United States
• Language: English

Related Subjects

42 ENGINEERING
420400
COEFFICIENT OF PERFORMANCE
FLUID MECHANICS
HEAT PUMPS
HEAT TRANSFER
HEAT TRANSFER AND FLUID FLOW
STIRLING CYCLE
THERMODYNAMICS