In this paper, the method of determining thermal contact resistance of wavy surfaces is discussed exactly. For determining the thermal contact resistance of real contacts, a new method has been presented. In this method, assuming a regular sinusoidal surface profile, the real contact area in terms of applied forces has been determined. Then thermal contact resistance has been calculated. Testing 6 kinds of insulator’s combinations with wavy surfaces has approved the reliability of the analysis. The results of experiments and analysis had good agreement with each other.

Nowadays, researchers have become interested in acquiring deeper knowledge concerning Thermal Contact Conductance (TCC) and Thermal Contact Resistance (TCR) existing among various types of metals during heat transfer occurrence in the nuclear reactor, thermal control system of spacecraft, and heat exchangers. In the present study, Artificial Neural Network (ANN) coupled with Multi-Layer Perceptron (MLP) modeling was utilized to predict transient temperature contour on various contacting surfaces such as at-at, at-cylinder, and cylinder-cylinder. In order to develop an accurate transient model, the parameters of metals including position, time, and roughness were used as input parameters, and temperatures of solid bodies were selected as the target parameter of the model. Modeling results demonstrate that ANN-based modeling outperforms other numerical methods in terms of accuracy. Moreover, values of Average Absolute Relative Deviation (AARD) and coefficient of determination (R2) for the overall data are 0. 056 and 0. 996, respectively, which prove the accuracy and robustness of the proposed model.

Thermal Contact Conductance (TCC) between an exhaust valve and its seat is one of the important parameters to be estimated in an internal combustion engine. An experimental study presented here to acquire temperature in some interior points to be used as inputs to an inverse analysis. An actual exhaust valve and its seat are utilized in a designed and constructed setup. Conjugate Gradient Method (CGM) with adjoin problem for function estimation is used for estimation of TCC. The method converges very rapidly and is not so sensitive to the measurement errors. Contact frequency is one the factors which have a significant influence on TCC. The results obtained from current inverse method as well as those obtained from linear extrapolation method show that the thermal contact conductance decreases as the contact frequency increases. The results obtained from both sets of results are also in good agreement.

In internal combustion engines, exhaust valve and its seat gain considerable temperature as the hot gases exit through them. So, the rate of heat transfer should be under control. In this study, the contact heat transfer coefficient has been estimated. An experimental study on an Air-Cooled internal combustion engine cylinder head has been considered. Using the measured temperatures of sensors located in specific locations of the exhaust valve and the seat and the method of linear extrapolation, the surface contact temperatures, and constant and periodic contact heat transfer coefficient were calculated. Also, a sensitivity analysis has been done to study the effects of different parameters of contact pressure, contact frequency, heat flux and cooling air speed on thermal contact conductance. The results show that between the major four considered parameters, the thermal contact conductance is more sensitive to the contact pressure, then the contact frequency, heat flux, and the cooling air speed are the most affecting parameters on thermal contact resistance.

Heat transfer has considerable applications in different industries such as designing of heat exchanger, nuclear reactor cooling, control system for spacecraft and designing of microelectronics cooling. As the surfaces of two metals contact each other, this issue becomes so crucial. Thermal contact resistance is one of the key physical parameters in heat transfer of mentioned surfaces. Measuring the experimental value of thermal contact resistance in laboratory is highly expensive and difficult. As an alternative, numerical modeling methods could be engaged. In this study, Inverse problem method solution is utilized as a proper method for estimation of thermal contact resistance value. In this order, three different configurations (flat-flat, flat-cylinder, and cylinder-cylinder) were utilized in two steady and unsteady state conditions to predict the value of thermal contact resistance. In conclusion, the final results establish the fact that the inverse problem method solution can predict thermal contact resistance values between contacting surfaces.