Question

Is a heat exchanger more efficient with dry air or humid air flowwing through it. Please explane.

Answer #1

Air is heated by exhaust gases that flow in a heat exchanger, as
shown in the figure. The
heat gained by the air is measured as 320 kW and the inlet air
temperature is 20°C.
Exhaust gases inlet state is 527°C, 822 kJ/kg, 64 m/s while the
exit state is 327°C, 607
kJ/kg, 78 m/s. If the flow rate of air is 10kg/s, determine the
flow rate of exhaust gases
and the exit temperature of air. [Cp-air = 1.005 kJ/kg...

Carbon dioxide gas flowing through a heat exchanger operating at
steady state is heated at an essentially constant pressure of 7 MPa
from 270C to 4270C. Neglecting kinetic and potential energy
changes, determine the heat transfer, in kJ per kg of CO2 flowing,
and compare with the result obtained using the ideal gas model.
Please be detailes with which TABLES were used. (Compare the
answers 610.5 kJ/kg. 402 kJ/kg (ideal gas)

Write down the total heat transfer resistance for a double-pipe
heat exchanger. Show how to convert from the total resistance to an
overall heat-transfer co-efficient and explain how flow regime may
affect overall heat transfer rate.

A concentric tube heat exchanger is comprised of a stainless
steel (ks = 40 W/mK) inner pipe, NPS 2- nominal schedule
40 size (corresponding to an inner diameter of 52.5 mm and an outer
diameter of 60.3 mm), and an outer stainless steel pipe of NPS
3-nominal schedule 40 (ID = 77.9 mm, OD = 88.9 mm). The heat
exchanger has an effective length of 35 m.
The inner pipe fluid is ammonia (?a = 0.3 · 10?6
m2/s, cpa...

Ammonia gas enters a reactor with 30% more dry air (no water
vapor) than is required for complete conversion (4NH3 +
5O2 --> 4NO + 6H2O). These gases enter the
reactor at 75c and exit at 600c. How much
heat is required per mole of ammonia fed?

An air-water vapor mixture containing 20% humidity at a dry
thermometer temperature of 40 ° C A tunnel is fed to the dryer by
being heated to 70 ° C. Red pepper samples It is dried in adiabatic
conditions. Leave the dryer system saturated For the mixing
air-water vapor mixture, find the following.
a) 10000 m3 of moist air at 40 ° C (air-water vapor mixture) warmth
Required heat to increase to 70 ° C
b) Air temperature at dryer...

A concentric tube heat exchanger is comprised of a stainless
steel (ks = 40 W/mK) inner pipe, NPS 2- nominal schedule
40 size (corresponding to an inner diameter of 52.5 mm and an outer
diameter of 60.3 mm), and an outer stainless steel pipe of NPS
3-nominal schedule 40 (ID = 77.9 mm, OD = 88.9 mm). The heat
exchanger has an effective length of 35 m.
The inner pipe fluid is ammonia (va = 0.3 ·
10-6m2/s, cpa =...

Steam at 400 psia and 50 percent quality is heated in a
steady-flow heat exchanger until it becomes saturated vapor. It is
then expanded isentropically through a turbine to 1 psia. This is
followed by cooling in a second heat exchanger and then isentropic
compression to the initial condition. Determine the Carnot
efficiency for the cycle and the net work output.

Air enters a counterflow heat exchanger operating at steady
state at 22°C, 0.1 MPa and exits at 7°C. Refrigerant 134a enters at
0.2 MPa, a quality of 0.21, and a mass flow rate of 30 kg/h.
Refrigerant exits at 0°C. There is no significant change in
pressure for either stream. (a) For the Refrigerant 134a stream,
determine the rate of heat transfer, in kJ/h (b) For the
refrigerant stream evaluate the change in flow exergy rate, in
kJ/h. (c) For...

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
is achieved by flowing hot oil at 400 DegreeC through the inner
pipe at a rate of 5 kg/s.
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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