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Simplified approach of predictions of thermal performance for counterflow fully-wet cooling coil

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Abstract

An innovative correlation associating the effectiveness (ε) of the fully-wet cooling coil with its number of transfer unit and vice versa is presented in this work. The thermal performance and design of fully-wet cooling coil can be predicted simply through those correlations. The analytical model was constructed on a basis of solving heat and mass transfer equation “enthalpy potential method” simultaneously coupled with the energy equations. The validity of the new correlations was tested by experimental reported in the available literature. A good agreement with deviation less than 10% was found during the comparison between the output results of the new correlations and those obtained from the literature. The main benefits of those new correlations (1) Its simplicity to be implemented through simple calculations of input parameters (2) It provides helpful guidelines for optimization of wet cooling coil performance during its operation coupling with the thermal system at which the coil is integrated.

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Fig. 1
Fig. 2

Abbreviations

Ai :

Inner surface area of the cooling coil (m2)

Ao :

Outer surface area of the cooling coil (m2)

b:

Slope of saturation air enthalpy line or Fictitious specific heat (kJ/kg K)

Cf :

Coolant fluid specific heat (kJ/kg K)

Cpa :

Air specific heat (kJ/kg K)

Cra:

Specific heat ratio (b/Cf)

ha :

Specific air enthalpy (kJ/kg)

hs :

Specific saturated air enthalpy (kJ/kg)

hsf :

Specific saturated air enthalpy at the coolant temperature (kJ/kg)

hsfin :

Specific saturated air enthalpy at the inlet coolant temperature (kJ/kg)

hsfout :

Specific saturated air enthalpy at the outlet coolant temperature (kJ/kg)

ma :

Air mass flow rate (kg/s)

mf :

Coolant fluid mass flow rate (kg/s)

mw :

Chilled-water mass flow rate (kg/s)

mra:

Ratio between air to coolant mass flow rate (ma/mf, –)

n:

Area index in enthalpy-area Eq. (14)

NTU:

Number of transfer unit (–)

Q:

Heat transfer (kW)

R :

Is defined as \( \frac{{\alpha_{o} }}{{\alpha_{i} }} *\frac{{\eta_{s} b}}{{Cp_{a} }} *\frac{{A_{o} }}{{A_{i} }} \)

Tdb :

Inlet air dry-bulb temperature (°C)

Tf :

Coolant fluid temperature (°C)

Tfin :

Inlet coolant fluid temperature (°C)

Tfout :

Outlet coolant fluid temperature (°C)

Ts :

Cooling coil surface temperature (°C)

Twbi :

Inlet air wet-bulb temperature (°C)

Wa :

Air humidity ratio (Kg/Kga)

Ws :

Saturated air humidity ratio (Kg/Kga)

Wsf :

Saturated air humidity ratio at the coolant temperature (Kg/Kga)

Wsfin :

Saturated air humidity ratio at the inlet coolant temperature (Kg/Kga)

Wsfout :

Saturated air humidity ratio at the outlet coolant temperature (Kg/Kga)

Ε:

Effectiveness (–)

Α:

Heat transfer coefficient (W/m2. °C)

δ:

Incremental

ήs :

Area-weighted surface fin efficiency (–)

a:

Ambient

am:

Mean value at the air-side

f:

Coolant fluid

i:

Inlet or inner

j:

Arbitrary position

m:

Mean

o:

Outside or outer

out:

Outside or outer

s:

Saturated or surface

sm:

Mean value at the coil surface

w:

Chilled-water

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Authors and Affiliations

  1. Department of Mechanical Engineering, Beirut Arab University, Beirut, Lebanon

    M. Khamis Mansour

  2. Department of Mechanical Engineering, Alexandria University, Alexandria, Egypt

    M. Khamis Mansour & M. A. Hassab

Authors
  1. M. Khamis Mansour
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  2. M. A. Hassab
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Correspondence to M. Khamis Mansour.

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Mansour, M.K., Hassab, M.A. Simplified approach of predictions of thermal performance for counterflow fully-wet cooling coil. Heat Mass Transfer 53, 2211–2217 (2017). https://doi.org/10.1007/s00231-016-1942-y

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  • DOI: https://doi.org/10.1007/s00231-016-1942-y

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