refrigeration properly explained

[poindexter]

I am still amazed that an article can be posted even though it contains incorrect and/or misleading information. Such is the case with the May 17 blurb on overclocking P4's to 4.1GHz. It states, "The compressor condenses the coolant to such an extent that it becomes liquid. The liquid coolant is applied through a copper core (vaporizer) that rests directly on the processor or the heat spreader. The heat from the CPU causes the coolant to vaporize and to return to the compressor. In the process it passes through the heat exchanger to dissipate the accumulated energy extensively." So here's how refrigeration really works-for all you true geeks out there. First, the compressor does not condense anything, that's why it's called "the compressor" and some OTHER part is called "the condenser". The compressor is simply a piston pump driven by an electric motor. It increases the pressure of the refrigerant gas. In Physics 101 we learn that temperature and pressure within a sealed system have a direct relationship: if you increase the pressure, the temperature will also increase; if you increase the temperature, the pressure will increase. The job of the compressor is to increase the temperature of the GAS. Why? So the condenser can change the state of the refrigerant from a GAS to a LIQUID. The condenser has hot, high pressure GAS coming from the compressor. As this hot gas runs through the tubes of the condenser, the heat is transferred to the fins, then to the surrounding air. If you transfer enough heat the GAS will CONDENSE to the LIQUID state, and this will happen with NO decrease in temperature. If you continue to transfer heat away from the circulating refrigerant you will end up with a temperature drop at the outlet of the condenser, however the refrigerant is now a LIQUID so there's negligible pressure loss. This LIQUID has a very very low "boiling point", for R-12 it's about -21F, for R-22 it's about -41F. In other words, if you were in Bismark, North Dakota and it was -65F outside [without the wind chill], you could actually pour liquid R-12 into a cup and it would just sit there, evaporating very very slowly. If you stuck your finger in the liquid, it would boil around your finger because the temperature of your finger is higher than the boiling point. You would also freeze your finger, so don't try this. This is exactly the same thing that would happen if you used water and a really hot metal rod, say fresh from a 400F oven. The water CHANGES STATE from a LIQUID to a GAS because of the transfer of heat energy from the rod to the water. When enough energy is transferred you will bridge the HEAT OF VAPORIZATION of the liquid. So we have this high pressure LIQUID refrigerant and we want to "cool" the CPU. Within a closed refrigeration system like these, the LIQUID is allowed to flow at a reduced rate [by various means-there's not enough room here] into THE EVAPORATOR. Usually the evaporator looks very much like the condenser-lots of fins and tubes. For chilling CPU's the evaporator is very very small and usually has no fins. As the LIQUID refrigerant enters the evaporator through the restriction two things happen. The pressure and temperature both drop, and once the LIQUID hits the hot area [heated by the CPU] it boils. The heat for this CHANGE OF STATE comes from the CPU. Now that the refrigerant is a GAS, it's routed back to the compressor for another lap. In a nutshell, all you're doing is removing heat from one spot [the CPU] and dumping it somewhere else [the air].

 

[Crashman]

And your point? I'm fairly sure most of those interested already knew this!

<font color=blue>Only a place as big as the internet could be home to a hero as big as Crashman!</font color=blue>
<font color=red>Only a place as big as the internet could be home to an ego as large as Crashman's!</font color=red>

 

[poindexter]

The point is clear, the article is flawed and should never have been published. It stated, "The compressor condenses the coolant to such an extent that it becomes liquid." This single sentence is incorrect for more than one reason thus it is wrong and misleading. The whole reason for publishing an article is to offer correct information to dispell incorrect information. If an article were published stating, "You can overclock your PC by connecting it to 240 volts AC instead of 120.", you would probably wonder how it ever made it to print. This is why there are Editors, though not all who hold that title are worthy.

 

[Crashman]

LOL, I forgot that you'd even mentioned any article. You should try deviding things into paragraphs. By the time I got to the end of what you'd wrote I thought you were simply describing how an evaporative cooling system worked.

<font color=blue>Only a place as big as the internet could be home to a hero as big as Crashman!</font color=blue>
<font color=red>Only a place as big as the internet could be home to an ego as large as Crashman's!</font color=red>

 

[Zeekfu]

roflmao crash.

I found it very informative.

peace

 

[ytoledano]

You should try deviding things into paragraphs.

He did, though he didn't devide it into too many...

Yea, though I walk through the valley of the shadow of death, I will fear no evil, for Thou art with me; Thy rod and Thy staff, they comfort me.

 

[poindexter]

Thanks! If I were writing an article I would have paid more attention to puerile details such as paragraph structure. This was simply a post that was composed as it was written. BTW-it's spelled d-I-v-i-d-i-n-g. Whenever I'm not sure I check spelling at dictionary.com. You can misspell your entry and it will give you several options.

 

[Crashman]

I'm a "professional" writer and I never check my spelling in here. I only check it when writing articles. My whole point for asking the information to be divided properly was that I lost the original intent of the post while reading the rest of the post.

<font color=blue>Only a place as big as the internet could be home to a hero as big as Crashman!</font color=blue>
<font color=red>Only a place as big as the internet could be home to an ego as large as Crashman's!</font color=red>

 

[poindexter]

So you don't check your spelling and I don't create paragraphs. If you lost your way in something as small as this I can't imagine the problems you have reading a book.

 

[Crashman]

hehe, I don't read books! I read articles, which usually have a summary, which usually restates the articles objective. I got through Uni based on my abilities to work with summations!

<font color=blue>Only a place as big as the internet could be home to a hero as big as Crashman!</font color=blue>
<font color=red>Only a place as big as the internet could be home to an ego as large as Crashman's!</font color=red>

 

[rower30]

Well, I don't seem to have Attention Deficit Disorder and thought he did just fine. You're on the right track if all people can manage to do is cut you down on paragraph, spelling and sentence structure.

A simple conservation of energy loop statement would help showing energy is not loosed or gained, either. This is where that expensive to run electric pump is coming into play. Pump up your car's tire with a bicycle pump and feel the "heat" in the compressed air at the shrader valve. Now depress the valve's release nipple and let the air out and feel your finger freeze as the air expands from inside the tire into the garage. No, it’s not liquid to gas but boy it sure still demonstrates the same principals. The energy you put in is lost again as it "cools" down coming back out.

 

[poindexter]

Thanks for the compliment. Conservation of energy does not apply here as energy is in fact lost. Consider the following-
Given: In a small room that is sealed off from external temperature changes sits an empty refrigerator. The door is open. The room temperature is 68 degrees F. The refrigerator is plugged in and turned on. After running constantly for 24 hours:
A) does the room temperature change?
B) Why?

Stay tuned to this channel for the correct answer and explanation.
Jeff

 

[Ned_Flanders]

die

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[Johanthegnarler]

What? Did you say DOom 3 in that large paragraph?

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46,510 , movin on up. 48k new goal. Maybe not.. :/

 

[rower30]

Never said, or meant to say, there isn't "loss" in the system. You do work up a sweat since YOU are the compressor pumping the tire up.

A} No the room temperature can't change.
B) Why? Because it's an internal system (what's going on in the gas evaporative loop cycle) + external system (what's going on in the electrical compressor cycle) in an internal only system (the room the fridge is in with an open door). The heat from the refrigerator's compressor, which is external energy loss applied to get the resultant internal evaporative gas loop, offsets the "refrigeration". So, the cold air out of the open fridge simply offsets the rooms heating from the hot air off of the compressor. If you placed the compressor OUTSIDE the room it is in, in your example, the room would cool. Or, to get a fridge itself to work you have to close it's door to isolate the internal and external conservation of energy loops from one another. And, they aren't really isolated, but just temporarily until the cool air is lost from inside the fridge to the outside word through convection. Why do you think your fridge keeps turning itself on.

I guess this means we can't cool of the whole world this way! Open all your refrigerators everybody!

 

[poindexter]

Perhaps I should have been more specific about which doors were open: the room door is closed and the room is sealed, the door to the refrigerator is open.
Answers:
A) The temperature of the sealed room will increase.
B) This is due to the heat lost in running the compressor. Even if the heat exchange in the refrigeration system was 100% efficient, which it is not, there is still the electrical power required to run the motor that operates the compressor. No motor is 100% efficient so there will be thermal losses here. There are also frictional losses in the compressor and these as well as the thermal losses in the motor will be dissipated into the ambient air. Additionally, if one chooses to ASSume that there are absolutely no losses to the motor or compressor there is the small light that remains on when the door is opened. Regardless of the type of light used it will produce heat. This was a final exam question in a college physics class: did YOU pass?