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A study on the effects of system pressure on heat and mass transfer rates of an air cooler

  • Thermal Engineering · Fluid Engineering · Energy and Power Engineering
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Abstract

In the present paper, the effects of inlet pressure on the heat and mass transfer rates of an air cooler are numerically predicted by a local analysis method. The pressures of the moist air vary from 2 to 4 bars. The psychrometric properties such as dew point temperature, relative humidity and humidity ratio are employed to treat the condensing water vapor in the moist air when the surface temperatures are dropped below the dew point. The effects of the inlet pressures on the heat transfer rate, the dew point temperature, the rate of condensed water, the outlet temperature of air and cooling water are calculated. The condensation process of water vapor is discussed in detail. The results of present calculations are compared with the test data and shows good agreements.

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Abbreviations

A :

Heat transfer area or area (m2)

C :

Dimensional parameter, see Eq. (2)

C p :

Specific heat (kJ/kg°C)

D h :

Hydraulic diameter of tube (m)

f :

Fouling coefficient (m2°C s/kJ)

H :

Length of fin (m)

h :

Heat transfer coefficient (kJ/s/m2)

h d :

Mass Transfer coefficient (kg/s/m2)

I, K :

Bessel function

i, j :

Index

i fg :

Latent heat of vaporization (kJ/kg)

J (s),J i (s):

Modified j-factors

k :

Thermal conductivity (kJ/s/m/°C)

L ent :

Entrance length of tube (m)

l :

Equivalent length of fin (m)

m, n :

Number of elements inx andy directions

Pr:

Prandtl number

\(\dot q\) :

Heat transfer rate (kJ/s)

r1,r2:

Inner and outer radius of circular fin (m)

Re:

Reynolds number

s :

Fin pitch (m)

T :

Hot air temperature

t :

Cold water temperature

U :

Overall heat transfer coefficient (kJ/s/m2/°C)

V :

Mean velocity (m/s)

W :

Humidity ratio (kg/kg) or width of continuous fin (m)

x :

Coordinate

y :

Fin spacing (m) or coordinate

Δx, Δy :

Size of element (m)

δ:

Fin thickness (m)

δQ :

Local heat transfer rate at element (kJ/s)

\(\delta \dot m\) :

Local condensation rate of water vapor (kg/s)

η:

Fin efficiency

0, 1:

Order of Bessel function

c :

Cold water

cs :

Cross sectional area

cont :

Fin-tube contact

f :

Fin

f, i :

Fin in sector

h :

Hot air

i, j :

Index

s :

Fin spacing or overall surface

w :

Heat transfer surface

References

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Authors and Affiliations

  1. Division of Mechanical and Information Engineering, Korea Maritime University, 606-791, Busan, Korea

    Hyung Ho Jung

Authors
  1. Hyung Ho Jung
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Correspondence to Hyung Ho Jung.

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Jung, H.H. A study on the effects of system pressure on heat and mass transfer rates of an air cooler. KSME International Journal 16, 696–702 (2002). https://doi.org/10.1007/BF03184819

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  • DOI: https://doi.org/10.1007/BF03184819

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