Cooling Tower Effectivity Calculation is described in this article. Cooling Tower plays a major position in Chemical Course of Trade. They reject process heat from the cooling water to ambiance and keep the water cool. The performance of the cooling tower relies on numerous parameters like Range & Approach. We shall see these terminologies intimately.
Cooling Tower Approach
The distinction between the Cold Water Temperature (Cooling Tower Outlet)
And ambient Wet Bulb Temperature is called as Cooling Tower Approach.
Method = Cold Water Temperature Wet Bulb Temperature
Cooling Tower approach is the better indicator of the efficiency.
Cooling Tower Range
The difference between the recent Water Temperature (Cooling Tower Inlet) Temperature and Chilly water (Cooling Tower Outlet) temperature is called Cooling Tower Range.
Range = Scorching Water Temperature Cold Water Temperature
Cooling Tower Efficiency Calculation
The calculation of cooling tower efficiency involves the Range and approach of the cooling Tower. Cooling tower efficiency is proscribed by the ambient wet bulb temperature. In the perfect case, the chilly water temperature will likely be equal to the wet-bulb temperature. That is practically not doable to realize. This requires very massive tower and results in huge evaporation and windage or drift loss leading to a virtually not viable solution. In observe, the cooling tower efficiency might be in between 70 to 75%.
Cooling Tower Efficiency =
(Sizzling Water Temperature Cold water Temperature) x one hundred/
(Sizzling Water Temperature Wet bulb temperature)
Cooling Tower Efficiency = Range/ (Vary + Approach) x one hundred
In summer time the ambient air wet bulb temperature raises when in comparison with winter thus limiting the cooling tower efficiency.
Different Cooling Tower Calculations
This consists of determination of cycle of focus, Evaporation loss, Drift or Windage Loss, Blow down water requirement makeup water requirement.
Cycle of Concentration
The cycle of concentration is a dimensionless number. It’s a ratio between parameter in Cooling Water to the parameter in Makeup water. It can be calculated from any the following formulae.
COC= Silica in Cooling Water / Silica in Make-up Water
COC = Ca Hardness in Cooling Water/ Ca Hardness in Make-up water
COC = Conductivity of Cooling Water / Conductivity of Makeup water
The cycle of concentration normally varies from three.Zero to 7.0 relying on the process Design. It is advisable to maintain the Cycle of concentration as excessive as doable to cut back the makeup water requirement of the cooling tower. At the identical time, the higher cycle of concentration will increase the dissolved solids focus in circulating cooling water which ends up in scaling and fouling of process heat transfer gear.
Draw off or Blowdown
Because the cooling water circulates the cooling tower part of water evaporates thereby increasing the entire dissolved solids in the remaining water. To control the Cycle of Focus blow down is given. Blowdown is the function of Cycle of concentration. Blowdown might be calculated from the formula:
B = E/ (COC-1)
B = Blow Down (m3/hr)
COC = Cycle of Concentration. Varies from 3.0 to 7.0 relying upon Manufactures Tips
Evaporation Loss Calculation
Evaporation Loss in the cooling tower is calculated by the next empirical equation.
E = zero.00085 x R x 1.8 x C
E = Evaporation Loss (m3/hr)
C = Circulating Cooling Water (m3/hr)
(Reference: Perry’s Chemical Engineers Hand Book )
Alternatively, The Evaporation loss might be calculated from the heat stability across the cooling tower. The amount of heat to be removed from Circulating water in accordance toQ = m CpDT isC x Cpx R .The quantity of heat eliminated by evaporative cooling isQ = m x Hv is E x HV
On Equating these two, we get
E = C x R x Cp / HV
C= Cycle of Concentration
R= Range in °C
Cp = Specific Heat = 4.184 kJ / kg / °C
HV= Latent heat of vaporization = 2260 kJ / kg
Windage or Drift Loss Calculation
Drift lack of the cooling tower is often supplied by the cooling tower manufacturer based mostly on the process design. If it isn’t out there it could also be assumed as
For Pure Draft Cooling TowerD = 0.Three to 1.Zero * C /a hundred
For Induced Draft Cooling Tower D = zero.1 to zero.3 * C /one hundred
For Cooling Tower with Drift EliminatorD = zero.01* C /100
Cooling Tower Mass Balance make-up water
Cooling tower mass balance provides an thought about make-up water requirement. Cooling Tower Makeup has to substitute the water losses ensuing from Evaporation, Windage and Blowdown.
M = E + D + B
M = Make up water Requirement in m3/hr
B = Blow Down in m3/hr
E = Evaporation Loss in m3/hr
D = Drift Loss in m3/hr
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