I am a retired technology teacher who is interested in building small Stirling engines. I want to be able to measure the heat flow through the displacer chamber of a test bed engine that I am building. The displacer chamber has an electrically heated hot end so measuring the heat input should just be a case of knowing the current and voltage supplying the heaters and multiplying them together .(actually not quite that simple as I plan to use PWM to control the heaters with a PID controller, but that’s another story.) The cold end of the chamber is cooled by water flowing through a series of passageways bored in the aluminium block. A long time ago when I was studying A level physics I remember measuring the thermal conductivity of copper using Searle’s bar apparatus and this is the sort of idea I want to use. I plan to measure the temperature of the water flowing in and out of the cooler and the rate of flow in kg per second. Knowing these and the specific heat capacity of water I should be able to calculate the amount of heat entering the cooler.
So, the problem is that I need to measure the temperature difference between the water flowing in the inlet and out the outlet. I don’t anticipate this difference will be very large, perhaps a few degrees Celsius at most so I will need some precision in these measurements. I am not interested in recording transient changes as the measurements will be made once the system has reached a ‘steady state’ so response time is not likely to be an issue. I think integrating a number of measurements taken over a period of time might help achieve the necessary precision.
What sensors would be suitable for this job. Would it be best to test a number of sensors and select a matched pair? The system will use ordinary water at atmospheric pressure so the temperature range must fall in the range 0 to 100 ⁰C.