Description of Analysis

 

The amount of energy being put into the tank water was first analyzed. This amount of energy was used as a base number to aim for when designing the heat exchanger. If this amount of energy is being put into the water, then a heat exchanger that can take out the same amount of heat would be ideal. Analysis of surface area, flow rate, and air flow where then performed.   

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One analysis that was done to find a parameter to fulfil a certain requirement was surface area. 20ft² of surface area was the amount of surface area calculated (A-5) to meet heating requirement of 20kW (A-1). 20ft² is too much area to fit into the requirement of the heat exchanger unit volume of 48ft³, 20ft² would require an excessive length of tube. Due to this, fins will be added to the heat exchanger tubes to increase surface area. Fins will be made of 6061 aluminum that are 1/16in thick. The length of the fins will be between 1/4in and 1/2in. 1/4in fin length gives 16ft² (under 18ft²) and 1/2in fin length gives 20ft² (over 18ft²). Using 1/4in fins will save 2592in² of aluminum than if 1/2in length fins were used, while only loosing 1% efficiency, but overall effectiveness reduces by 30%. The heat transfer rate with 1/4in fins is calculated to be 19.4kW vs. 5kW if no fins were to be used. 

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