Operating characteristics of a loop heat pipe-based isothermal region generator

An isothermal region of a finite size is an important requirement for precision metrology and its related industries. In this work, a loop heat pipe (LHP)-based isothermal region generator was devised in which a high speed vapor flow region of the LHP was utilized to achieve the isothermal region. To this end, a stainless steel LHP employing water as a working fluid was designed and fabricated. In particular, an annular type vapor flow region was configured in the vapor transport line to accommodate the isothermal region with dimensions of 50 mm × 360 mm (diameter × height). Temperature uniformity testing demonstrated that the maximum temperature difference and the effective thermal conductivity of the isothermal region at the maximum heat load were 0.56 °C and 311 000 W/(m K), respectively. The temperature uniformity improved with increasing mass flow rate and showed a dependence on the speed of the working fluid. The steady state operating temperature of the isothermal region ranged from 47.1 °C to 64.0 °C with temperature hysteresis at low heat loads. Details of the design and operating characteristics of the LHP-based isothermal region generator are provided and discussed.