Refrigeration power calculation

[nikos_abel]

Hi guys

This must be my 1st post, at least for a few years

Is there somewhere a way to calculate what power an evaporator or a condenser is?

For instance, I have a condenser 4/20x300 fin 2,5 with a 16W/D250 (27°) fan.

How can I covert this to f.i. 1/4Hp?

It is a troubling question for me, first of all because I am not a refrigeration engineer but a mechanical engineer
and then 'cause I still haven't figured out what f.i. (again) an 1/4Hp refrigerating power means for a compressor, the refrigerating power stated by the manufactures in Watts does not compute!!!!

Thank you in advance!!!!

[nikos_abel]

Anybody help? Please!!!!!

Just a link would suffice!!!!!!

Thanks

[Magoo]

Hi Nikos,
The formula is a complex calculation. Comes down to total effective surface area and heat transfer factors which includes coil air dwell time, volumes and velocities.
Most coil manufacturers here will state capacity in degrees K'. Example: evaporator 3500watts at 6'K system TD. TD is evaporating temp of liquid, and the air on temperature. Or air on at -18'C and evap temp -24'C
Kueba Germany used to publish the formula, I will see if I still have it somewhere.

[nikos_abel]

Thamks a lot, i wiil be waiting.

[Peter_1]

Nikos, you will have just a rough guess, capacity is indeed as Magoo stated related to some factors but we don't know the k- factor of your coil, only the manufacturer can give you this.
I would like to add to Magoo's parameters, straight fins or waffled fins, rectangular pattern or not, rippled fins or not, bypass factor of the coil, air volume of the fans,...
To give you a rough guess: the cm³ of the coil - so a coil of 100 x 100 x 10 cm gives 100000 cm³ - will condense +/-17 kW (/5.8) with an air speed over the coils of at least 3 m/s at a DT of 15K (2 mm fin spacing, rectangular pattern 35 x 35 mm and 3/8 or 1/2" tube)

If you need 10 K for 17 kW, then you need +/- a 150000 cm³ coil volume. That's how we make them and we make +/- 5 to 8 OEM condensers/year (market trucks)

The capacity of any coil is for 80 to 90% determined by it's surface, all the rest comes from fans, internal volume, rippled fins or not,...
When I compare condensers from different brands, the main decision factor for me will always be the heat exchanger surface surface, then the air volume, then internal volume, then weight. Of course comparing at the same DT.
And always going for 10 K at max ambient at full load.

[nikos_abel]

Hi again, I was on vacation with no internet access (thank god), but I'm back now, for good!

Peter, the information you give me is somewhat awesome.

But the I'm just trying to figure out how some folks "name" the heat exchangers in fractions of Hp. At least, this is how here in Greece the technicians ask for them, though no one has gave me a satisfying explanation.

I'm just trying to determine the connection.

Thanks again