Raise evap temp 1 degree better effic

[gwm121]

the ample questions for 2079 say if evap temp raised 1 degree c eff improve 3% where can i get some background reading to understand this or can someone expalin please??

[Josip]

Hi, gwm121

welcome to RE forums...

the ample questions for 2079 say if evap temp raised 1 degree c eff improve 3% where can i get some background reading to understand this or can someone expalin please??

sorry my English is not that good ... but, please, search RE forums ... keywords like cop, c effective, energy saving, condensing temp/press .... etc.... and for sure you'll find something about ... something about min/max dt over heat exchanger - evaporator or condenser ... why to increase suction temp/press and decrease condensing temp/press to get better COP i.e. decrease energy consumption... limits regarding sizes of evaporators/condensers due to manufacturing costs ...

or you can wait .... for sure someone will come to explain it in better English language than my

Best regards, Josip

[RANGER1]

The refrigerant is also more dense as pressure /temp increases .
This will mean compressor can pump more volume of gas , so increases its efficiency .
Basically you want highest suction pressure / temp to achieve room/product temp .

[littleyapper]

it's a bit of a buzz word at the moment "suction optimisation" have a look on the danfoss web site ... at least i think thats what you are looking for

[Yuri B.]

if evap temp raised 1 degree c eff improve 3% where can i get some background reading to understand this or can someone expalin please?

Imagine a task of transferring of 10 packs from one room to another. By that, the first pack weighs 10 kilograms, the second weighs 10% more than the first, the third 10% more than the second, etc.

One begins with the lightest pack, then carry the pack which is 10% heavier, etc.

By every go one makes 10% more work but his muscles may consume, let's say, only about 3.3% more energy. 10/3.3 = about 3% increase in efficiency.

[Peter_1]

This is for me not a good question: it depends on so many things
1. Refrigerant used
2. Evaporating pressure
3. In which region are we working: freezing, cooling or AC application? Extremely important
4. There's nothing said about the condensing pressure.

Possible good answers could be the following but only to judge if the candidate gets the point of this question:
1. 3% (the good answer according to those who made it but not necessarily the only one)
2. -3%
3. 10%
4. 0%

But giving 2 %, 2.5%, 3% and 3.5% as possible good answers isn't correct. I can give pressures and/or situations where all answers will be true.

I've seen other F-gas questions which aren't correct for me.

[Peter_1]

The same is also valid when lowering HP

[El Padre]

Hi GWM121,

I think that you need to plot it on a PH chart to clarify, on the right hand side you will see lines of constant specific volume, as the specific volume increases through lower suction pressures or excess superheat the mass flow reduces and so does system efficiency.

Cheers

[Gary]

Assuming a basic system, there are two opposing forces in the evaporator which balance against each other. The heat load pushes the pressure/temperature up while the compressor pulls the pressure/temperature down.

If the pressure/temperature rises as a result of increased heatload the system runs more efficiently, moving a lot more heat for a little more energy.

If the pressure/temperature rises as a result of the compressor not pulling as hard as it should (broken valves for example) then the efficiency drops like a rock, moving a lot less heat for a little less energy.

Its not the bang and its not the buck. Its the bang for the buck.