(Invited) Peltier Supercooling with Isosceles Current Pulses: Cooling an Object with Internal Heat Generation

Monday, 2 October 2017: 09:00
Chesapeake F (Gaylord National Resort and Convention Center)
A. J. Piggott (Applied Thermoelectric Solutions LLC, Michigan Technological University) and J. S. Allen (Michigan Technological University)
Applying an electrical current pulse enables a transitory state in which the cold junction of a Peltier couple reaches temperatures below that obtained with a steady-state optimal current. This is known as supercooling. This supercooling is followed by a period of superheating. It has been shown for isosceles triangle shaped current pulses with the optimal combination of pulse-height and duration, the sum of supercooling and superheating can provide a net cooling advantage. In most cases, supercooling has been studied as a standalone couple and not as a system. The objective of this paper is to gain insight about the sensitivity of system performance metrics of COP, power consumption, cold junction cooling rate (Qc) and average mass temperatures during pulsed operation when used to cool a mass with internal heat generation. To accomplish this, a comprehensive parametric study was performed that includes pulse-height, pulse duration, thermal interface resistance, thermal effusivity of the cooled mass, heat spreader thermal conductivity, and internal heat generation of the cooled mass were varied. The temperature distribution inside the thermoelement during pulsing, and the effects of continuous pulsing at an optimized pulse-height and duration were also investigated. The study was accomplished with a system model that utilized electrical-thermal analogies in SPICE. It was demonstrated that Qc over an entire pulse event can be improved over Imax steady operation but not steady Iopt operation. Qc can be improved over Iopt operation but only during the early part of the pulse event. COP is reduced during pulse operation due to different time constants of Qc rate and power consumption. During part of the transient, lower performance interface materials can improve Qc and COP.