Thermal product of type-E fast response temperature sensors

Abstract

This paper provides practical data for thermal product values of different scratched temperature sensors that can be used for accurate transient heat transfer measurements under hypersonic flow conditions. The effect of using different scratch techniques (abrasive papers and scalpel blades) to form the sensor's junction is investigated. It was observed that the thermal product of a particular sensor depends on the Mach number, junction scratch technique, junction location and enthalpy conditions. It was demonstrated that using different scratched technique would produce different thermal product values.

Development of a Fast-Response Diamond Calorimeter Heat Transfer Gauge

“…The uncertainty in the heat flux measured by the thermocouples is dominated by uncertainty in the value of effective thermal product used: the real value depends on the exact location of the thermocouple junction, how the junction was made, and the time-scale of interest. Estimates of measurement uncertainty on a time-scale of milliseconds for similar gauges are at least 10 % [12,14]. On a time-scale of tens of microseconds, which is of interest for the current study, the thin layer of electrical insulation between the two metals can affect heat conduction through the gauge and decrease the effective thermal product by as much as 30 % [9], leading to an over-prediction in surface heat flux measurement.…”

“…Additionally, the assumption of heat conduction into a homogeneous medium most often used to calculate heat flux from a temperature measurement [11] is not valid on a tens of micro-second time-scale [9,12]. At longer time-scales reports of thermal product values for similar gauges vary by as much as 15 % [13,14], and can vary by as much as 20 % depending on the method used to form the junction [12]. Good electrical grounding is required to avoid interference from ionised flows due to exposed Table 1 Details of current types of DHTG.…”

Coaxial Thermocouples for Heat Transfer Measurements in Long-Duration High Enthalpy Flows

“…The influence of the temperature increase on the thermophysical parameters of type-E thermocouples has been extensively investigated by several researchers [ 12 , 22 , 23 ]. We used the equation developed by Mohammed [ 12 ] to determine the specific heat and thermal conductivity of chromel and constantan with increasing temperature, as well as the thermophysical parameter fitting equation for stainless steel used by Mills [ 24 ]. The changes in the effective thermal effusivity versus the temperature of chromel, constantan, and stainless steel are shown in Figure 9 .…”

“…Li also investigated the influencing mechanism of the junction size, the thickness of the insulating layer, and the effect of thermal conductivity on the heat transfer measurements. Marineau [ 9 ], Buttsworth [ 11 ], Mohammed [ 12 ], and Chen [ 13 ] conducted calibration experiments on the effective thermal effusivity of coaxial thermocouples; large differences were observed in the thermal effusivity for different junction grinding processes. Wang [ 14 ] researched the impact of different materials on transient heat transfer measurements obtained from coaxial thermocouples; measurement errors of up to 20% were obtained in 100 ms measurement periods.…”

A Fast-Response Calorimeter with Dynamic Corrections for Transient Heat Transfer Measurements

“…In such facilities, where the effective test time is on the order of milliseconds, the heat flux rate is derived from the transient temperature monitored at selected points on the model with fast response testing technology. Generally, the techniques can be divided into two categories; the first is based on heat flux sensors, such as resistance thermometers [5][6][7][8], thermocouples [9][10][11][12][13], and calorimeters [14][15][16][17], and the second is based on non-intrusive techniques such as temperature-sensitive paint [18,19] and thermography [20,21]. However, each technique has its own benefits and challenges.…”