The role of expandable thermal systems in improving performance of thermal devices

In this work, heat transfer through various expandable thermal systems is analyzed theoretically. These systems include single layered expandable insulation system, expandable surfaces like balloons and microchannels supported by flexible seals including both soft seals and flexible complex seals. It is found that heat transfer in expandable thermal insulation decreases as the ratio of the thermal conductivity of the gas to its gas constant (k/R) decreases. Heat convection over expanding spherical surfaces is found to be proportional to (T-s/T-infinity)(2/3)(T-S - T-infinity) rather than (T-S - T-infinity) for rigid spherical surfaces and that flexible microchannels, especially those, supported by flexible complex seals are preferred to be used at lower values of Reynolds number, Prandtl number and aspect ratio with uniform temperature at the inlet. Finally, expandable thermal systems can pave the way for a new class of thermal devices with favorable thermal characteristics. (C) 2006 Elsevier Masson SAS. All rights reserved.