Published versio

Heat flux measurement is used in the field of fluid mechanics and heat transfer to quantify the transfer of heat within systems. Several techniques are in common use, including: differential temperature sensors such as thermopile, layered resistance temperature devices or thermocouples and Gardon gauges; calorimetric methods involving a heat balance analysis and transient monitoring of a representative temperature, using, for example, thin-film temperature sensors or temperature sensitive liquid crystals; energy supply or removal methods using, for example, a heater to generate a thermal balance; and, finally, by measurement of mass transfer which can be linked to heat transfer using the analogy between the two. No one method is suitable to all applications because of the differing considerations of accuracy, sensitivity, size, cost and robustness. Recent developments including the widespread availability and application of thin-film deposition techniques for metals and ceramics, allied with advances in microtechnology, have expanded the range of devices available for heat flux measurement. This paper reviews the various types of heat flux sensors available, as well as unique designs for specific applications. Critical to the use of a heat flux measurement technique is accurate calibration. Use of unmatched materials disturbs the local heat flux and also the local convective boundary layer, producing a potential error that must be compensated for. The various techniques in common use for calibration are described. A guide to the appropriate selection of a heat flux measurement technique is provided according to the demands of response, sensitivity, temperature of operation, heat flux intensity, manufacturing constraints, commercial availability, cost, thermal disturbance and acceleration capability for vibrating, rotating and reciprocating applications.

No abstract

For some aerospace and automotive applications, it has been difficult to produce instrumentation for the harsh environments encountered. Problems include high temperatures, high centrifugal forces, corrosive exhaust gases, and potential damage from high velocity particulates. This paper reports the design and development of a thin film instrument for temperature monitoring. The device comprises two gold tracks for use as excitation leads, and a platinum resistance element, both applied to a chemically robust electrical insulator. The gold tracks were deposited using a commercial gold ink consisting of a solution of a gold mercapto balsamate complex in an organic solvent. Most of the organic solvent evaporates when the ink is applied, and the residual organic material is removed on fusion. Gold is the metal of choice because of its resistance to oxidation and the chemical and thermal stability of the films produced. Gold ink is particularly easy to apply, the process is readily controlled and no expensive equipment is required. This paper describes the application of the gold ink and the analysis of the films produced, along with a description of the sensor fabrication and performance.

No abstract