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WorksheetsLecture 7 - Double Pipe Heat Exchanger
Total questions: 10
Worksheet time: 5mins
Identify whether below examples are categorized as heat exchanger:
(i) Condensers and evaporators in refrigeration units
(ii) Evaporator of an ice plant and milk chiller of a pasteurizing plant
(iii) Automobile radiators and oil coolers of heat engines
i only
i and ii
i and iii
i, ii, and iii
What type of flow arrangement is shown in the Figure?
Counter flow
Parallel flow
Crossflow
Shell and tube
Which flow type of heat exchanger is illustrated in this Figure?
Parallel flow
Counter flow
Crossflow
Shell and tube
Identify which assumptions are commonly used in the heat exchanger analysis
(i) Kinetic energy is negligible
(ii) Potential energy is negligible
(iii) Mass flow rate of each fluid remains constant
(iv) Constant velocity at any inlet or outlet
(v) Temperature at any inlet or outlet remain the same
i, ii, and iii
i, ii, iii, and iv
i, ii, iv, and v
All the assumptions are correct
Choose the correct expression for the logarithmic mean temperature difference (LMTD) for parallel flow heat exchanger, where:
ΔTi= temperature difference between hot and cold fluid at inlet of heat exchanger
ΔTe= temperature difference between hot and cold fluid at exit of heat exchanger
ln (ΔTi– ΔTe)
ln (ΔTe – ΔTi)
(ΔTi– ΔTe) / ( ln (ΔTe / Δti))
(ΔTi– ΔTe) / ( ln (ΔTi / Δte))
For the same inlet and exit temperatures of two fluids, the LMTD for counter flow is always
smaller than LMTD for parallel flow
greater than LMTD for parallel flow
same as LMTD for parallel flow
Can be either smaller or greater
Choose the correct statement for the parallel flow heat exchanger.
The exit temperature of hot fluid is always equal to the exit temperature of cold fluid.
The exit temperature of hot fluid is always less than the exit temperature of cold fluid.
The exit temperature of hot fluid is always more than the exit temperature of cold fluid.
We cannot predict comparison between exit temperatures of hot fluid and cold fluid
Fouling factor of a heat exchanger can be calculated by
[Thermal resistance of heat exchanger without scaling] – [Thermal resistance of heat exchanger with scaling]
[Thermal resistance of heat exchanger with scaling] – [Thermal resistance of heat exchanger without scaling]
[Thermal resistance of heat exchanger without scaling] x [Thermal resistance of heat exchanger with scaling]
[Thermal resistance of heat exchanger without scaling] + [Thermal resistance of heat exchanger with scaling]
A parallel flow heat exchanger always requires more heat transfer area than the counter flow type heat exchanger.
True.
False.
For specified inlet and outlet temperatures, the log mean temperature difference (LMTD) is always larger than the the arithmetic mean temperature difference (AMTD).
True.
False.
