Heat transfer in a water-water heat exchanger - Lab Report Example

The heater and main switch was turned on and the water temperature controller was set at 60oc.The hot water flow rate and cold water flow rate were set to 50g/sec and 15g/sec respectively. The flow rates and stream temperature were monitored making sure that there was temperature stabilization and there was no drift of flow rate. The temperatures were then recorded in the table with the following headings; Repeat with cold water flows of;25g/sec,40g/sec and set the hot water temperature to 40oc and repeat step 2 and 3 The cold water supply was interchanged and the horse connection was returned.

At this point, the exchanger had been configured with co-current flow. There was a single set readings made with hot water at 60oc, Vhot=50g/sec and Vcold=40g/sec. The results were recorded in the table The energy gained by cold stream Qc and energy lost from the hot stream was calculated for each run with the use of equations 1 and 2 in the theory sections. It was noted that the indicated flow values V, was to be multiplied by 0.001 to give mass flows (F) in S.I unit of Kg s-1 Basing on the results, it was observed that when the flow rate of the cold water was increased in the first 3, the T6 that is the midpoint also increased.

The reading for T1 was never the same as the initial temperature. It is evident that heat transfer rate could be calculated with the use of heat transfer coefficient log mean temperature difference and total area (Shah and Joshi 1987; Gnielinski 1976). The same kind of results is seen to hold for counter flow and parallel heat exchangers whereby there is change in temperature for both fluids. It is not easy to analyze the cross-flow heat exchangers and there is a good estimation to the actual condition when the log mean temperature difference is used in case one stream never changes to a large extent in terms of temperature (Techo, Tickner and James 1965; Moffat 1988).

It is not easy to solve heat exchanger problems in