Home > categories > Machinery & Equipment > Heat Exchanger > Heat exchanger question (HW)?

Heat exchanger question (HW)?

I did a lab where water is passing through the shell and steam is passing through the tubes. One thing that was noted was the temperature of the steam out is less than steam in. Its expected that the steam just condenses without a temperature change. Lab question is asking for a possible reason why this doesn't' happen. I'm confused /blanking out on this. In a heat exchanger....shouldn't you expect that if the water stream heats up then the steam would cool down. Any any possible reasons for this too would be appreciatedthanx


It is not clear from your question if the steam is coming out of the exchanger as steam or steam condensate. If it is condensate, then it can easily be colder than the steam coming in. The water is simply removing more heat from the steam than just the heat of condensation. This is call sub-cooling. If it is still all steam, then there has to be a drop in pressure on the steam side to be sufficient for the outlet steam temperature to be lower than the inlet steam temperature. If you plot the inlet and outlet conditions on a Mollier diagram, you can see exactly what is happening.
#What about the water temperature and pressure?That is in shell side. # I hope that the flow will be counter current. Check that the themodynamic steam trap is installed or not . If installed then check that it is functioning ok or not. Prime the system [steam side] by opening by-pass valve in outlet line and then take the steam trap in line. Check the flow and pressure.If required increase the flow. What are the condition of baffles? Is the HE new or old? Take the pressure test for any tube leakage.

Share to: