Calorimetry of heat pump system using ultra-fine fluorescent wires and PIV

Abstract

To understand transport phenomena of heat and fluid flow in various fields of engineering, it is essential to develop experimental methods for measuring the temperature field in a fluid flow. The two-color laser-induced fluorescence (LIF) technique is suitable for performing temperature measurements of water flow. This technique eliminates the influence of laser intensity fluctuations observed in the single-color LIF technique, which is a significant source of error in temperature measurement. However, the two-color LIF technique has not been applied to air flow. Although this problem was solved by developing a technique for spraying fluorescent dye mists, steadily maintaining the non-uniform diameter of the tracer particles of a fluorescent mist, which is thought to influence the evaluated temperature, has been difficult because the mist consistently descends and mixes with the surrounding flows. In this study, we propose a temperature measurement method that uses ultra-fine fluorescent wires to reduce the wire diameter to much less than that of a thermocouple. This is possible because its structure is simple, and any material can be used for the wire. Hence, ultra-fine wires whose Reynolds number is less than 1.0 can be selected. This means that turbulent flow is not generated downstream of the wire and that its wake is negligibly small. Furthermore, the number of wires decreases because a line profile of temperature can be measured using only one wire.