Question

A double pipe heat exchanger consists of 1" Sch 40 steel pipe (Do = 1.315 in., Di = 1.049 in., Δx = 0.133 m) inside a 2" Sch 40 Steel pipe (Di = 2.067 in.) is used to heat water from 25 °C to 40 °C using hot air entering at 200 °C. Water flows in countercurrent through the inner tube at 1000 kg/hr while air flows through the annulus at 5000 kg/hr. For the steel: Thermal conductivity = 45 W/m-K Air properties at the bulk temperature: Cp = 1046 J/kg-K, k = 0.035 W/m-K μ = 2.507 x 10^-5 kg/m-s, and ρ = 0.727 kg/m^3 Water properties at the bulk temperature: Cp = 4184 J/kg-K - Determine the LMTD if the outlet temperature of the Air is 170 °C - Determine the Reynolds Number of Air - Determine the outlet temperature of the Air (°C) - If h of Water = 185 and h of Air = 2500, Determine the value of Uo or Ui - Determine the cross-section of the annulus (in mm^2). - If Ui = 175, ΔTlm = 145 °C, determine the length of the heat exchanger (in in)

          A double pipe heat exchanger consists of 1" Sch 40 steel pipe (Do = 1.315 in., Di = 1.049 in., Δx = 0.133 m) inside a 2" Sch 40 Steel pipe (Di = 2.067 in.) is used to heat water from 25 °C to 40 °C using hot air entering at 200 °C. Water flows in countercurrent through the inner tube at 1000 kg/hr while air flows through the annulus at 5000 kg/hr.
For the steel: Thermal conductivity = 45 W/m-K
Air properties at the bulk temperature: Cp = 1046 J/kg-K, k = 0.035 W/m-K
μ = 2.507 x 10^-5 kg/m-s, and ρ = 0.727 kg/m^3
Water properties at the bulk temperature: Cp = 4184 J/kg-K

- Determine the LMTD if the outlet temperature of the Air is 170 °C
- Determine the Reynolds Number of Air
- Determine the outlet temperature of the Air (°C)
- If h of Water = 185 and h of Air = 2500, Determine the value of Uo or Ui
- Determine the cross-section of the annulus (in mm^2).
- If Ui = 175, ΔTlm = 145 °C, determine the length of the heat exchanger (in in)

Added by Lisa W.

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