Water (cp = 1.0 Btu/lbm·°F) is to be heated bysolar-heated hot air (cp = 0.24 Btu/lbm·°F) in a double-pipecounter-flow heat exchanger. Air enters the heat exchangerat 190°F at a rate of 0.7 lbm/s and leaves at 135°F. Waterenters at 70°F at a rate of 0.35 lbm/s. The overall heat transfercoefficient based on the inner side of the tube is given tobe 20 Btu/h·ft2·°F. Determine the length of the tube requiredfor a tube internal diameter of 0.5 in.
Energy transfer
The flow of energy from one region to another region is referred to as energy transfer. Since energy is quantitative; it must be transferred to a body or a material to work or to heat the system.
Molar Specific Heat
Heat capacity is the amount of heat energy absorbed or released by a chemical substance per the change in temperature of that substance. The change in heat is also called enthalpy. The SI unit of heat capacity is Joules per Kelvin, which is (J K-1)
Thermal Properties of Matter
Thermal energy is described as one of the form of heat energy which flows from one body of higher temperature to the other with the lower temperature when these two bodies are placed in contact to each other. Heat is described as the form of energy which is transferred between the two systems or in between the systems and their surrounding by the virtue of difference in temperature. Calorimetry is that branch of science which helps in measuring the changes which are taking place in the heat energy of a given body.
Water (cp = 1.0 Btu/lbm·°F) is to be heated by
solar-heated hot air (cp = 0.24 Btu/lbm·°F) in a double-pipe
counter-flow heat exchanger. Air enters the heat exchanger
at 190°F at a rate of 0.7 lbm/s and leaves at 135°F. Water
enters at 70°F at a rate of 0.35 lbm/s. The overall heat transfer
coefficient based on the inner side of the tube is given to
be 20 Btu/h·ft2·°F. Determine the length of the tube required
for a tube internal diameter of 0.5 in.
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