# Exit temperature of cooling pond

1. Sep 25, 2015

### Charles CL

Dear All,

Referring to the subject above, I have found the calculation of heat load based on [Lawrence,K.W., Norman, C. P. & Yung, T. H. (2005). Advanced Air and Noise Pollution Control. Totowa: Humana Press.]

My cooling pond system:
1. Purpose: cooling POME temperature from 70 to 40 degree C.
2. Medium: palm oil mill effluent (POME),
3. Surface Pond Area: 800 m2,
4. Average wind speed: 4 km/h (no shelter/open pond),
5. Humidity: 88% RH,
7. Room temperature: 30 - 35 degree C.

It is using the equilibrium temperature to estimate the exit temperature of WATER from the pond. However, mine system is using POME which came after the palm oil extraction from the fresh fruit bunch (FFB).
The real situation is, this created some problem due to a layer of oil on the medium as the extraction process is not that efficient. The temperature was not able to reduce after a retention time of 2 days, and the current temperature is at 45 degree C which is above the mesophilic temperature for the bacteria to be alive and active.
Could anyone advice on how to calculate the exit temperature based on the situation above as the POME has a layer of oil insulating on it?
Back to the calculation get from the book, it has not included the heat load for once-through cooling ponds, but only included it for completely recirculating type of cooling pond. Mine system is plug flow system, which it would be the same as once-through system.

Besides, i can't find any information regarding to the density of POME. If anyone know, kindly share at here.

Charles CL.

2. Sep 25, 2015

### Bystander

You're stuck with convective cooling only (no evaporation).

3. Sep 27, 2015

### Charles CL

Hi Bystander, thank you for the reply.
Convection,
q = hA(T0 - T1).

What about the density of the POME? Do you have any idea on it?
I

4. Sep 28, 2015

### Charles CL

Dear Bystander,

Enclosed with the excel calculation sheet that i had done previously.
Notice that, the formula used was for conduction and evaporation, where Bowen's conduction-evaporation coefficient was applied. However, no heat load applied in the calculation.

For apply of convection only,
the convection coefficient will be calculated as attached excel file (calculation template from engineeringtoolbox.com).
With the convection coefficient calculation, i see no wind speed parameter involved. May you please advice on how to get to the temperature of the POME with the convection coefficient?

#### Attached Files:

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• ###### natural convection coefficient.xlsx
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5. Sep 28, 2015

### Bystander

If the object is to keep the POME at a temperature less than 40 C, you will probably get more satisfactory results adding some sort of agitation (aeration from below the pond surface, or sprinkler/mist) than trying further modification of heat transfer software that's not terribly well adapted to the problem.

6. Oct 6, 2015

### Charles CL

Thank you for the sharing of idea.
It is a good idea of adding sprinkler/mist as it does not involved additional electrical consumption.
How about the further modification of heat transfer calculation from the data sheet?

7. Oct 6, 2015

### Staff: Mentor

Last edited: Oct 6, 2015
8. Oct 6, 2015

### Staff: Mentor

@Charles CL -- Welcome to the PF. Can you say more about this project? From your PF Profile page, it looks like you have recently graduated from university and have been given this project. What resources do you have available at your new company? What safety and health regulations do you need to keep in mind in this project?

9. Oct 6, 2015

### Charles CL

Hi Berkeman,

I'm working on biogas project, where we are using bacteria to generate the gas and turn it into electricity. The cooling pond functioned to cool down the temperature of the incoming POME (waste) which come from the palm oil mill factory after the extraction of the palm oil. This POME is used as the "food" for the bacteria to grow and produce the gas. The entry temperature to the cooling pond was recorded at 70 degree C, which is very high for the mesophilic bacteria to be alive and active, and it is going to be cooled down into 35 to 40 degree C. However, our site engineer reported that the pond has exceeded the ideal temperature approaching to 50 degree C, which is not good for system.

Therefore, i'm going to find out the source of problem. It might be caused by the design overlook from the consultant, or it might be caused by the civil work. I'm working out of this calculation is to see the level of significant of the area of the pond towards the cooling effect, and the contribution of effect of the oil layer towards the surface temperature of the pond.