Comparison of Two Potassium-Filled Gas-Controlled Heat Pipes

Abstract

Calibration by comparison of platinum resistance thermometers and thermocouples requires transfer media capable of providing very good short-term temperature uniformity and temperature stability over a wide temperature range. This paper describes and compares the performance of two potassium-filled gas-controlled heat pipes (GCHP) for operation over the range from 420 °C to 900 °C. One of the heat pipes has been in operation for more than 10 years having been operated at temperature for thousands of hours, while the other was commissioned in 2010 following recently developed improvements to both the design, assembly, and filling processes. It was found that the two devices, despite differences in age, structure, number of wells, and filling processes, realized the same temperatures within the measurement uncertainty. The results show that the potassium-filled GCHP provides a durable and high-quality transfer medium for performing thermometer calibrations with very low uncertainties, over the difficult high-temperature range from 420 °C to 900 °C.

Sodium-Potassium Alloy Heat Pipe under Geyser Boiling Experimental Study: Heat Transfer Analysis

“…The working temperature of high temperature heat pipes is higher than 750 K. Sodium, potassium and other alkali metals are often used as working fluid for high temperature heat pipe because of their high boiling temperature, low saturation pressure, high latent heat of vaporization and high heat transfer performance. Alkali metal heat pipes have been used in many high temperature applications such as high temperature isothermal heater [4], thermometric calibration system [5,6], solar energy utilization system [7,8], residual heat removal system [9][10][11][12], high temperature thermal management [13][14][15] and so on. The alloy of suitable ratio of sodium and potassium is liquid at room temperature, so the sodium-potassium (Na-K) alloy heat pipe has great advantages in cold-start and working fluid filling.…”

Isothermal performance of a temperature comparison source using potassium concentric annular heat pipe

“…Figure 3B presents the size and structure of heating furnace. The potassium CAHP was placed horizontally in the middle of the heating furnace, and other places in the furnace were filled with insulation The operating temperature range of potassium heat pipe is about 400 C to 1000 C, 9,18 and depends on the temperature required for thermocouple calibration, the heating temperatures in this study were set at 400 C, 500 C and 600 C. The temperature distribution at 0 to 16 cm from the bottom of four metering wells was measured. One thermometer as a reference thermometer is always placed at the bottom of the metering well, and the other as a measuring thermometer to measure the temperature at different positions.…”

“…The working fluid remains saturated during the working process of the heat pipe, so heat pipes also have high isothermal performance, and heat pipes are also used in the field of isothermal heating 6,7 and metering. 8,9 The concentric annular heat pipe (CAHP) is composed of two pipes, and the sealed area between the two concentric pipes is the working fluid space. Nouri-Borujerdi et al 10 developed a numerical model of vapor flow in CAHP using fast difference scheme based on the SIMPLE algorithm.…”

“…Due to the strong heat transfer ability and simple structure, heat pipes are used in many fields, such as high heat transfer fields, 1,2 thermal management fields, 3,4 thermal protection fields, 2,5 etc. The working fluid remains saturated during the working process of the heat pipe, so heat pipes also have high isothermal performance, and heat pipes are also used in the field of isothermal heating 6,7 and metering 8,9 …”

Numerical Study on the Effects of the Wick Structure of an Annular Heat Pipe on the Isothermal Performance

“…Although the isothermal performance, temperature stability and service life of the gas-control heat pipe are very good [10], the pressure control system is complex and the heat pipe manufacturing is difficult [11]. Annular heat pipes are also widely used in the field of measurement.…”