Can anybody explain why my numbers are not equally out? At work, I am trying to determine the heat transfer taking place in a water cabinet. Both loops have water in them. There is a counter current flow heat exchanger where the transfer takes place. I take the temperature measurements with a Microscanner D1001 IR thermometer. With this device I contact the surface of a pipe and take the measurement. I take about 3-5 measurements and average them out. I do this at the same spot on the pipes for the other inlet/outlet to the heat exchanger. Each pipe has the same diameter and the same material. (I know this is not a 100% correct method, but I am hoping it gets me close enough, because the thermocouple connected to the pipes are not calibrated. I have done this step about 50 times to get enough values to minimize any outliers. Next I take the flow on the two loops. From there I use the equation: Heat tranferred = specific heat of water * flow * delta temperature. (I have no issues with the units). When I compare the two loops, the numbers are off on average of 5kW (the average of the loops is (30kW and 25kW). The same loop is almost always higher. And this is the same case when I take the measurements off of duplicate machines. I got my data from over 5 water cabinets that were the same. Why are my two loops not equally? Any guesses? Thanks!