Investigating the effect of coolant’s heat transfer type on thermostat placement

Abstract

Nowadays, modern engines control a wide range of parameters in order to meet desired functions and standards. Measurement of mechanical systems has long been an issue for engineers and researchers. Sensors are the devices which monitor the mentioned parameters. Therefore, the accuracy of sensors is an important consideration. Extracting the exact temperature of the coolant (coolant content: 50% water and 50% ethylene glycol) in engine cooling system by the sensors and also thermostat depends largely on their correct placement. The task of controlling coolant flow rate and engine temperature is done by the thermostat mounted in the cooling system. In the present work, the coolant temperature behavior has been investigated due to inappropriate design of the thermostat housing in a gasoline engine. Considering the importance of the cooling issue, the problem has been solved by two methods, namely test and numerical solution. The results obtained from these methods have had a good convergence with each other. Warm-up test results show that thermostat is not capable of sensing the real temperature of the coolant. According to the results, a design change has been made in the thermostat housing. The new sample of thermostat housing has been tested and also numerically analyzed. A good agreement between the test results and numerical solution has been observed. The opening temperature and time of the thermostat in new housing have been reduced by more than 9 °C and nearly 149 s (about 2.5 min), respectively.