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Unformatted text preview: Plate Heat Exchanger By David Taylor ChE 325 2/19/08 Ms. Loveland, We experimented with the plate heat exchanger in this lab. Through our data we have found that with increasing flow rates, the heat transfer coefficient also increases. For both a constant cold and hot water stream, we varied the opposite stream eight times and collected data in the form of inlet and outlet temperatures from the heat exchanger. We also found that the relationship between 1/U and 1/V is linear. We concluded that the relationship followed the Wilson method and that it was acceptable to use that for further comparisons. Our results confirm what was expected from this experiment, that higher flow rates, both hot and cold, will produce higher heat transfer coefficients. Although the flow rates were rather unsteady, my partner and I did what we could to maintain a consistent table of data as the temperatures were unsteady also. After much consideration, that was the only possible chance for any error that may appear through our experiment. Sincerely, David Taylor Introduction and Background The plate heat exchanger experiment was performed to investigate how to maximize the amount of heat transfer as efficiently as possible, using different flow rates of hot and cold water. Many industries use plate heat exchangers at low temperatures and low pressures to do this. Our plate heat exchanger was comprised of eight corrugated stainless steel plates. Between the plates, alternating streams of hot and cold water run counter currently. As the streams flow continuously, heat is transferred from the hot stream to the cold stream. When the water exits the heat exchanger, the cold stream is warmer than the cold inlet and the hot stream is cooler than the hot inlet. In order to find out how much heat is transferred across the heat exchanger, many things need to be calculated such as, the Reynolds number, the Nusselt number, the Prandtl number, the heat transfer coefficient of both hot and cold streams, and the overall heat transfer coefficient. First, we must find the Reynolds number using this equation: Re = (1) Where is density in g/cm^3, v is the mean fluid velocity in m/s, D is the hydraulic diameter in cm, and μ is the fluid viscosity in Pas. After the Reynolds number is calculated, if is determined to be turbulent flow, we can use the Buonopane equation to find the Nusselt number: Nu=0.254( )( (2) Where Pr is the Prandtl number, determined by the temperature of the fluid. The constants are determined by experimental procedures. Now we can find the convective heat transfer coefficient, h in W per m^2K: h= (3) where k is the conductive heat transfer coefficient and x is the diameter. To calculate the overall heat t ransfer coefficient in W per m^ 2K, U, we use the Wilson...
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This note was uploaded on 03/26/2008 for the course CHEM E 325 taught by Professor Loveland during the Spring '08 term at Iowa State.
 Spring '08
 Loveland
 The Land

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