Water-Water Exchanger - Heat Transfer in a Water-Water Pipe...

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Heat Transfer in a Water-Water Pipe Heat Exchanger Eric Burbach, Alex McKinney, Mason Merritt, Jasa Zunaibi University of Nebraska-Lincoln
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Table of Contents Abstract: 3 Introduction 3 Experimental Apparatus 8 Safety 11 Operating Procedures 11 Personal and Chemical Safety 11 Process safety 12 Results and Discussion 12 Calculating Overall Heat Transfer Coefficient (U) 13 Determining Accuracy of Constructed Models 13 Estimating Overall Heat Transfer Coefficient (U) 14 Energy Conservation Validity 14 Effects of Operating Conditions 16 Flow Configuration 16 Flow Rate 17 Inner Pipe Inlet Temperature 18 Overall Heat Transfer Coefficient Primary Dependency 19 Conclusions and Recommendations 20 References 22 Appendix 23 Appendix A 23 Appendix B 23 Appendix C 23 Appendix D 23 Appendix E 23 2
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Abstract: The objective of this experiment was to model the temperature distribution and overall heat transfer coefficient, U, for a cocurrent and countercurrent water- water heat exchanger and observe how different conditions affect it and the heat transferred. In this experiment, two streams of water were flown through a piping system with a known inlet and outlet temperatures and flow rates. The pipes were 1.5 in type L hard temper copper tubing for the annulus and 1 in type L hard temper copper tubing inner pipe sections. The annulus section had an outer diameter of 1.625 in with 0.06 in wall thickness and the inner section had a outer diameter of 1.125 in with 0.05 in wall thickness. The exchanger is split into four section of contact between the inner and annulus pipe of 19 ft each. Inlet flow and temperatures were varied to observe the change in the temperature, heat transferred, and overall heat transfer coefficient values . The heat formula was used to find the energy transferred throughout the exchanger and empirical formulas were used to find the predicted U. The measured U was calculated using nonlinear regression in combination with the steady state energy balances for cocurrent and countercurrent streams. An approximately equal amount of energy from the hot stream transferred to the cold stream regardless of the operating conditions. The calculated Q values between the two pipes varied by less than a percent in all trials. Countercurrent flow transferred more energy in every trial ran.The measured cocurrent U ranges from changing flow by 54.24 lb/min and temperature by 14 were 532 W/m 2 K and 316 W/m 2 K respectively. The measured countercurrent U ranges from changing flow by 52.61 lb/min and temperature by 13 were 1431 W/m 2 K and 282 W/m 2 K respectively. These ranges show that U is a strong function of the flow rate. Heat transfer was not a function of position for countercurrent flow because of a constant temperature gradient. In this experiment, Q is a strong function of position for cocurrent flow and begins to level off after 10 meters because of the constantly decreasing temperature gradient.
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  • Spring '18
  • Hunter Floodman
  • Heat Transfer, countercurrent flow, Cocurrent flow

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