method to design air cooled condenser

Hi there

sometime back i asked u people to tell me the way 2 design air cooled condenser . reply was not encouraging let me tell u how we design it

below is data given in MBH/sq.ft multiply it with Heat rejection ratio factor and multiply by face area u select.

u will get the capacity of coil.


note...all these data are experimental and are valuable in many ways as we do all designing based on it



if data below isnot clear then see the attachment


TOTAL HEAT REJECTION MBH/FT²

Following data is based on

Entering air temperature= 95°F
Condensing temperature= 125°F

Copper tube 3/8” Aluminum fins with plane tubes

2 ROW CONDENSER COIL PERFORMANCES

AIR VELOCITY @ COIL FPM
FPI 300 400 500 600 700
12 5.0 5.54 6.21 6.84 7.5
14 5.6 6.0 6.82 7.49 8.09
16 6.5 6.8 7.42 8.15 8.50

3 ROW CONDENSER COIL PERFORMANCES

AIR VELOCITY @ COIL FPM
FPI 300 400 500 600 700
12 6.6 7.5 8.5 9.4 10.12
14 7.5 8.0 8.93 9.86 10.90
16 8.2 8.6 9.36 10.32 11.68

4 ROW CONDENSER COIL PERFORMANCES

AIR VELOCITY @ COIL FPM
FPI 300 400 500 600 700
12 7.5 8.52 9.95 11.12 12.16
14 8.0 9.4 10.54 11.9 12.90
16 8.5 9.10 11.13 12.67 13.64

Abbasi,

There isn't a simple formula for this. A formula which will work for one manufacturer will not work for another one.
It depends all the way how you fabricate the coil: thickness fins, contact area of the fins on the tubes, thickness copper tubes, ripple fin tubes, alignement of the copper lines, bypassfactor, straight fins or curved, flow pattern in the condenser, ...
Calculating the U factor for a given evaportar is not that difficult if you have the surface area of the fins, the flow parameters of the air and the refrigerant,...
But you can't use this factor for yourselves because you never can make the coil the same way they do.
If we need a coil, we give the working specs and it's the manufacturer who must calculate the coil so that he meets our specs.
Many coil manufacturers have software to do this.

We use for simulating the software (free) of Lemmens engineering here in Belgium. I also saw other software in the past doing the same thing. (Heatcraft perhaps..)

For static evaporators like used in counters, we use a simple table from our manufacturer Heynen here in Belgium which is accurate enough for our applications. www.heynen-cool.com and then their catalog (or ebook) of Glacial. It's in Dutch and French I think.

We sometimes uses condensers on the roof of a truck which must pass under bridges. Some years ago, we made for example one of +/- 8 m (+/- 25 ft) long with a height of only 15 cm (+/- 6 inch) en 3 feet width. He couldn't pass otherwise under some bridges. There were +/- 8 fans on it. (will take a picture of it the next time I see this truck again)

I just took the specs of some standard condensers of Kuba and Goedhart and looked in the tables what fin area and airflow they had. We ordered one with 20 % more fin area to be sure that he was big enough. It's still working.
How the tubes are arranged and what size they have (3/8 or 1/2 or 5/8) is not important, it's mainly 1st the fin area and 2nd the airflow.

Hi abbasi
what is the MBH unit?
your data is from manufacturer or other？
I work to design dehumidifying coil recently and get two software (one is from Tongji Uni\other is from USA coil). The result is only for reference if you manufacture the coil by yourself. But it can give you a direction. the exact result should get by test. Now I set up a simple test to confirm my dehumid coil manufactured according to Heatcraft design. I don't expect if there is any formula to solve engineering issue directly.

MBH means 1000 Btu/hr






1 MBH= 1000 Btu/hr



Also can u mail me ur software @ email

engineerali@gmail.com

my tables are purely based on experimental results i obtained from different coil manufacturers



regards

Ali

Hi abbasi
iam a new user of this
i have some question releated refrigeration
Q.1 HOW WE DESINGE THE EVAPORTOR AND WHAT IS THE FACTORS ?
I WANT TO DESIGN A NEW REFRIGERATOR
COULD U PLEASE HELP ME
THANKS
JAHANGIR AHMAD KHAN