Question

A heat exchanger uses saturated steam at 375 K to heat cold water entering at 280 K and leaving at 301 K. Only the latent heat of vaporization is removed from the steam, i.e. the steam is condensed and saturated water exits the exchanger. (a) What is the LMTD for a counter-current heat exchanger? (b) What is it for a parallel heat exchanger (c) If the counter-crrent heat exchanger has a duty(Q) of 81000 kJ/hour and an overall heat transfer coefficient (U) of 500 kJ/sq.m K, what is the calculated heat transfer area in square meters? (d) If the parallel heat exchanger has the same, what is the calculated heat transfer area in square meters?

Answer #1

A heat exchanger uses saturated steam at 375 K to heat cold
water entering at 280 K and leaving at 301 K only the latent heat
of vaporization is removed from the steam. i.e. the steam is
condensed and saturated water exit the exchanger. a) what is the
LMTD for a counter current heat exchanger? b) what is the LMTD for
a parallel or cocurrent heat exchanger? c) if the counter current
heat exchanger has a duty (Q) of 81000...

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oC. Assuming an overall heat transfer coefficient of
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are of thin wall construction with D = 30 mm and the steam
condenses on their outer surface. The heat transfer rate that must
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Problem #1
Saturated steam at 300°C is used to heat a counter-currently
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a) Draw a diagram of the process.
b) Calculate the required flow rate of the entering steam in
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Cold water enters a counter flow heat exchanger at 20ºC at a
rate of 10 kg/s, where it is heated by a hot water stream that
enters the heat exchanger at 80ºC at a rate of 2 kg/s. Assuming the
specific heat of water to remain constant at Cp=4.18 kJ/(kg.ºC),
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Two products enter an indirect contact heat exchanger that uses
steam for heating. The first product which contains 15% solids
enters at the rate of 3 kg/hr and at 10 °C. The second stream which
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Oil enters a counterflow heat exchanger at 600 K with a mass
flow rate of 10 kg/s and exits at 350 K. A separate stream of
liquid water enters at 20°C, 5 bar. Each stream experiences no
significant change in pressure. Stray heat transfer with the
surroundings of the heat exchanger and kinetic and potential energy
effects can be ignored. The specific heat of the oil is constant,
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If the designer wants to ensure...

Oil enters a counterflow heat exchanger at 525 K with a mass
flow rate of 10 kg/s and exits at 275 K. A separate stream of
liquid water enters at 20°C, 5 bar. Each stream experiences no
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surroundings of the heat exchanger and kinetic and potential energy
effects can be ignored. The specific heat of the oil is constant, c
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Oil enters a counterflow heat exchanger at 525 K with a mass
flow rate of 10 kg/s and exits at 275 K. A separate stream of
liquid water enters at 20°C, 5 bar. Each stream experiences no
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surroundings of the heat exchanger and kinetic and potential energy
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A counter current double pipe heat exchanger is used to boil but
not superheat water at 100 DegreeC at rate of about 0.1 kg/s. This
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Latent heat of water: 2265 kJ/kg
Heat capacity of water: 4180 J/kgK
Heat capacity of the oil: 1800 J/kgK
What is the temperature of he hot oil leaving the heat
exchanger?
What is the overall heat...

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