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  • Heat Exchangers

    • Overall Heat Transfer Coefficient and Heat Transfer Rate Page
      An organic vapor is condensing on the outer surface of a 5 m long copper (\(k=400\) W/[m.K]) tube having 25 mm OD and 20 mm ID. The heat transfer coefficient of the vapor is 1500 W/(m2.K). The coolant enters at 300 K and leaves at 325 K. The coolant side heat transfer coefficient is 2500 W/(m2.K) and the fouling coefficients on the inner and outer surfaces are 2000 W/(m2.K) and 4000 W/(m2.K) respectively. The vapor condenses at 355 K. Determine:
      1. the overall heat transfer coefficient based on outer surface area ______ W/(m2.K)  (round off to 1 decimal place)
      2. the heat transfer rate _________ W (round off to 1 decimal place)
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    • Overall Heat Transfer Coefficient - Ex-1 Page
      NecatiOzisik-11-7
      Determine the overall heat transfer coefficient \(U_o\) based on the outer surface of brass tube with \(D_i=2.5\) cm and \(D_o=3.34\) cm [\(k=110\) W/(m.oC)] for the following conditions: The inside and outside heat transfer coefficients are, respectively, \(h_i=1200\) and \(h_o=2000\) W/(m2.oC); the fouling factors for the inside and outside surfaces are \(F_i=F_o=0.00018\) m2.oC/W.
      ______ W/m2 (round off to 1 decimal place).
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    • Overall Heat Transfer Coefficient - Ex-2 Page
      BT-2022-3
      For a double-pipe heat exchanger, the inside and outside heat transfer coefficients are 100 and 200 W/(m2.K), respectively. The thickness and thermal conductivity of the thin-walled inner pipe are 1 cm and 10 W/(m.K), respectively. The value of the overall heat transfer coefficient is ________ W/(m2.K) (Choose from: 0.016 / 42.5 / 62.5 / 310)
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    • Length of Double Pipe Heat Exchanger Page
      BT-2021-52
      Milk flowing through a stainless steel inner tube (40 mm inner diameter) of double tube-type heater is to be heated from 10oC to 85oC by saturated steam condensing at 120oC on the outer surface of the inner tube. Total heat transferred (\(Q\)) is 146200 kCal/hr, and the overall heat transfer coefficient is 750 kCal/(hr.m2.oC). The total length of the heating tube in m (rounded off to one decimal place) is _________
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    • LMTD of Heat Exchanger Page
      ME-2019-S2-46
      Hot and cold fluids enter a parallel flow double tube heat exchanger at 100oC and 15oC, respectively. The heat capacity rates of hot and cold fluids are \(C_h=2000\) W/K and \(C_c=1200\) W/K, respectively. If the outlet temperature of the cold fluid is 45oC, the log mean temperature difference (LMTD) of the heat exchanger is ______ K (round off to two decimal places).
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    • Heat Transfer between Jacket Fluid and Stirred Tank Page
      1990-14-ii-ht
      A hot fluid flows through a well mixed stirred tank which is provided with a cooling jacket. The fluid in the cooling jacket can also be assumed to be well mixed. Calculate the heat transfer area (in m\(^2\)) of the jacket required given the following data:
      Hot fluid:
      Flow rate, \(W_h\) = 50 kg/sec; \(T_{hi}\) = 205\(^\circ \)C; \(C_{Ph}\) = 2 kJ/kg.\(^\circ \)C.
      Cold fluid:
      Flow rate, \(W_c\) = 100 kg/sec; \(T_{ci}\) = 25\(^\circ \)C; \(T_{co}\) = 45\(^\circ \)C; \(C_{Pc}\) = 4 kJ/kg.\(^\circ \)C.
      \(U\) = 2.5 kW/m\(^2\).\(^\circ \)C
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    • Heat Transfer Area of Cooling Jacket Page

      Alternate solution to the previous problem

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    • LMTD between Tank Contents and Coil Fluid Page
      1988-4-c-ht
      An organic liquid is cooled continuously in a stirred tank by water flowing through a cooling coil. The organic liquid may be considered to be perfectly mixed. Inlet and outlet temperatures of the organic liquid are 50\(^\circ \)C and 30\(^\circ \)C respectively and those of the cooling water are 20\(^\circ \)C and 25\(^\circ \)C. Calculate the log mean temperature difference (in \(^\circ \)C) for heat transfer through the coil.
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    • Heating of Liquid in Tank by Steam Flow through Coil Page
      CoulsonRichardsonV4-9-71
      Liquid is heated in a vessel by means of steam which is supplied to an internal coil in the vessel. When the vessel contains 1000 kg of liquid it takes half an hour to heat the contents from 293 to 368 K if the coil is supplied with steam at 373 K. The process is modified so that liquid at 293 K is continuously fed to the vessel at the rate of 0.28 kg/s. The total contents of the vessel are always maintained at 1000 kg. What is the equilibrium temperature which the contents of the vessel will reach, if heat losses to the surroundings are neglected and the overall heat transfer coefficient remains constant? ________ K (round off to 1 decimal place)
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    • Exit Temperature of Coolant from Steam Condenser Page
      ME-2021-S2-44
      A shell and tube heat exchanger is used as a steam condenser. Coolant water enters the tube at 300 K at a rate of 100 kg/s. The overall heat transfer coefficient is 1500 W/(m2.K), and total heat transfer area is 400 m2. Steam condenses at a saturation temperature of 350 K. Assume that the specific heat of coolant water is 4000 J/(kg.K). The temperature of the coolant coming out of the condenser is ______ K (round off to the nearest integer).
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    • Fouling Factor of Double Pipe Heat Exchanger Page
      Students must
      Mark as done
      Incropera6E-11-16
      A counterflow, concentric tube heat exchanger is designed to heat water from 20 to 80oC using hot oil, which is supplied to the annulus at 160oC and discharged at 140oC. The thin-walled inner tube has a diameter of \(D_i=20\) mm, and the overall heat transfer coefficient is 500 W/(m2.K). The design condition calls for a total heat transfer rate of 3000 W.

      What is the length of the heat exchanger? _______ mm

      After 3 years of operation, performance is degraded by fouling on the water side of the exchanger, and the water outlet temperature is only 65oC for the same fluid flow rates and inlet temperatures. What are the corresponding values of the heat transfer rate? ____ W, the outlet temperature of the oil? ____ oC, the overall heat transfer coefficient? ____ W/(m2.oC), and the water side fouling factor? _____ \(\times10^{-4}\) m2.oC/W.

    • Overall Heat Transfer Coefficient of 2-8 Shell-and-Tube Exchanger Page
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    • Effectiveness NTU Method - Formula and Steps Page
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    • Effectiveness of Heat Exchanger - Ex-1 Page
      ME-2014-S2-48-ht
      In a concentric counter flow heat exchanger, water flows through the inner tube at 25\(^\circ \)C and leaves at 42\(^\circ \)C. The engine oil enters at 100\(^\circ \)C and flows in the annular flow passage. The exit temperature of the engine oil is 50\(^\circ\)C. Mass flow rate of water and engine oil are 1.5 kg/s and 1 kg/s, respectively. The specific heat of water and oil are 4178 J/kg.K and 2130 J/kg.K, respectively. The effectiveness of this heat exchanger is ________ .
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    • Effectiveness of Heat Exchanger - Ex-2 Page
      Incropera6E-11-18
      Consider a concentric tube heat exchanger with an area of 50 m2 operating under the following conditions:
      Hot fluid Cold fluid
      Heat capacity rate (kW/K) 6 3
      Inlet temperature (oC) 60 30
      Outlet temperature (oC) - 54
      1. Determine the outlet temperature of the hot fluid. _____ oC
      2. What is the type of heat exchanger operation?
        1. counter flow
        2. cocurrent flow
        3. can't tell from the available information
      3. Calculate the overall heat transfer coefficient._____ W/(m2.oC)
      4. Calculate the effectiveness of this exchanger._____
      5. What would be the effectiveness of this exchanger if the length were made very large? ______
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    • Effectiveness of Heat Exchanger - Ex-3 Page
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    • Exit Temperature for the given UA Page
      CoulsonRichardsonV4-9-12
      In an oil cooler, water flows at the rate of 360 kg/h through a metal tube of outer diameter 19 mm and thickness 1.3 mm, along the outside of which oil flows in the opposite direction at the rate of 0.075 kg/s. If the tubes are 2 m long and the inlet temperatures of the oil and water are 370 K and 280 K respectively, what will be the outlet oil temperature? The coefficient of heat transfer on the oil side is 1.7 kW/(m2.K) and on the water side 2.5 kW/(m2.K) and the specific heat of the oil is 1.9 kJ/(kg.K).
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