ChemicalEnggLAB/HeatExchanger/Thermodynamics

This report represents the outcome of heat exchange via 4 tubes that are fitted within the shell with four thermocouples to determine the temperature for every pass, two passes for the hot water (in/out) and two for the cold water (in/out). The experiment was commencing according to the amount of hot and cold water that was supplied to the inputs of the heat exchange. The supply was managed by the use of taps that would restrain or allow the gush of water. The temperature for the inputs was constant in the most of the 5 runs while the outputs had been changed due to heat exchange occurring within the shell. Hot water had lost temperature while cold water had gained temperature.

An experiment was set up to resolve the energy losses that affect the hot and cold water, by using thermodynamic laws. During the experiment the water gush rates were measured carefully and the data had been collected and entered to allow the calculations of the energy losses that came out. Finally, it was discovered the heat had been exchanged from the hot into the cold to maintain the temperature inside the shell.

Contents:

ii

The exchanger consists of a number of tubes that sit inside a shell that allows cold water to flow through them. Hot water flow through the bordering shell and the two fluids exchange heat. Heat exchanger can come in various forms and as such can have many different motives. A radiator in a car and a boiler in a steam engine are both heat exchanger with the radiator cooling the engine, and the boiler exchanging raw materials into steam that can be used for power generation. The heat exchanger that has been used in this experiment was a basic shell and tube style as shown in figure 1. A Jenco digital thermometer and Jenco thermocouple switches are used in the heat exchanger set up to allow to calculate the measurements for the experiment. Flow meters fitted on the inlet of hot and cold water taps are used to change volume flow rates.

The aim of the report is to evaluate the heat losses that came out for the hot water. The experiment will carry of recording temperatures and flow rates and then calculating other possible factors that may cause heat loss.

1) Be familiar with the different part of the experimental.

2) Turn on the cold and hot water taps.

3) Turn valves for the cold water at an initial flow rate (approximate 15 L/min for cold water) Make sure that all the water passes through the flow meters (turn off one of the valves in each water supply line)

4) Water for couple of minutes before reading the data.

5) Take the temperature reading for the thermocouples 1 to 5 by press the Jenco thermocouple buttons.

6) Repeat steps from 3) to 5) for 5 different flow rate combinations.

EXPERIMENTAL DATA:

Room temperature: 15°C

a) Mass and Energy equations:

,

b) Energy Loss:

c) Enthalpy changes for run 3:

i. Method 1:

From steam table

(A-4)

ii. Method 2:

d) Theoretical value of :

= 26.4

There is the different between the resulting temperature and the data collection which is 1.6. This suggests that there is a little bit of heat loss

During a heat exchanger experiment, heat exchange has been observed between two water tubes baring different temperature. It has been noticed that the heat exchange occurred due to the conduction from source with more energy than that of the source baring less energy. Thus, it prevails that the loss of energy in hot water was not due to the heat energy but from the cold water and mechanics of flow rate. In addition, it is the same as the second law of thermodynamics in which the cold temperature adapts to the warm temperature.

For industrial applications the shell and tube heat exchange are preferred widely as they are much efficient in converting between two different fluids temperatures. The more mass two fluids have the more heat is exchanged between fluids (which are exposed to each other in the exchanger) as the exchange area is increased. Therefore, the plate heat exchanger is considered more efficient in terms of cooling hot water. For measuring the rate of flow of fluids per meter in our (shell and pipe) heat exchanger two flow meter is useful in this regard. On the other hand thermocouples are preferred for the temperature readings. The procedure is generally consists of water supply and meter readings for five different water flow rates. According to the calculations the heat transmission between the fluids is equal to the total heat quantity after the loss of heat in the system.

5