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Heat and Mass Transfer

, Volume 53, Issue 4, pp 1391–1403 | Cite as

Design and experimental analysis of counter-flow heat and mass exchanger incorporating (M-cycle) for evaporative cooling

  • Omar KhalidEmail author
  • Zubair Butt
  • Waqas Tanveer
  • Hasan Iqbal Rao
Original

Abstract

In this paper, the functioning of dew-point cooler is improved in terms of its thermal effectiveness. For this reason, a heat and mass exchanger has been designed by using a counter-flow pattern incorporating Maisotsenko cycle (M-cycle) having effective absorbing material called Kraft paper on wet channel side and improved width to height ratio. Experimentation has been performed under various inlet air working parameters such as humidity, velocity and temperature in addition with changing feed water temperature. The results from the experiments specify that the dew-point and the wet-bulb effectiveness is achieved between 67–87 % and 104–120 % respectively. Analysis is performed with temperature variation between 25 and 45 °C at different absolute humidity levels ranging from 14.4 to 18 g/kg, while the inlet air velocity is varied between 0.88 and 1.50 m/s. Thus, the working ability of the improved design has been found 5 % more effective in terms of wet bulb effectiveness as compared to previous counter-flow designs.

Keywords

Humidity Ratio Evaporative Cool System Mass Exchanger Direct Evaporative Cool Feed Water Temperature 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Nomenclature

DB

Temperature dry bulb (°C)

r

Working-to-intake air ratio (kg/kg)

Cpm

Moist air specific heat capacity (kJ/kg K)

h

Specific enthalpy (kJ/kg)

t

Temperature (°C)

WB

Temperature wet bulb (°C)

Across

Cross sectional area of channel (m2)

Mass flow rate (kg/s)

d

Cross sectional diameter of extension duct (m)

hm

Coefficient mass transfer (m/s)

hw

Heat transfer coefficient between water film and channel walls (W/m2 K)

h

Coefficient heat transfer (W/m2 K)

hfg

Enthalpy of saturated vapor (kJ/kg)

hm

Coefficient mass transfer (m/s)

IEC

Indirect evaporative cooler

Lc

Characteristic length (m)

mw

Water mass flow rate (kg/s)

mwk

Working air mass flow rate (kg/s)

Nu

Nusselt number

QT

Total heat tranfer (W)

Qcooling,r

Cooling capacity of evaporative cooler (W)

Ql

Latent heat

Qs

Sensible heat

tdb

Temperature dry bulb of intake air (°C)

tdb,2

Temperature dry bulb of supply air (°C)

tdb,3

Temperature dry bulb of exhaust air (°C)

tdp

Dew-point temperature of intake air (°C)

ti

Measured temperature in each smaller area (°C)

tp,f

Process air dry bulb temperature (°C)

Ps

Saturation pressure (Pa)

Pw

Vapor pressure corresponding to wet bulb temperature (Pa)

w

Moisture content

v2

Supply air velocity (m/s)

v3

Exhaust air velocity (m/s)

V2

Airflow rate of supply air (m3/h)

RH1

Relative humidity of intake air (%)

RH2

Relative humidity of outlet air (%)

RH3

Relative humidity of exhaust air (%)

Greek symbols

ɛ

Effectiveness

ω

Humidity ratio (kg/kg)

ɛwb

Effectiveness wet bulb

ɛdp

Effectiveness dew point

pf

Density of air (kg/m3)

pw

Water film density (kg/m3)

uf

Dynamic viscosity of air at the mean temperature of working air (N s/m2)

\({\emptyset }\)

Relative humidity

uw

Air dynamic viscosity at the temperature of channel wall (N s/m2)

Subscripts

a

Air

in

Inlet

wk

Working air

out

Outlet

dew

Dew point

wb

Wet bulb

Notes

Acknowledgement

This work was supported and funded by the Mechanical Engineering Department of University of Engineering and Technology, Taxila Pakistan. This is gratefully acknowledged.

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Copyright information

© Springer-Verlag Berlin Heidelberg 2016

Authors and Affiliations

  • Omar Khalid
    • 1
    Email author
  • Zubair Butt
    • 2
  • Waqas Tanveer
    • 1
  • Hasan Iqbal Rao
    • 1
  1. 1.Department of Mechanical EngineeringUET TaxilaTaxilaPakistan
  2. 2.Department of Mechatronics EngineeringUET TaxilaTaxilaPakistan

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