Chiller questions

[Soxhlet]

What does he want to know? I was just summoned?

[sidco]

It appears @ravspd is using name tagging in a reply to let @Killbill know what to check out, as the kids do on the insta these days.

[ravspd]

lmao yes, sorry.

[cyclopath]

So I haz summoned you again? But with out the name calling. @DrJosh should get involved!

[Soxhlet]

I’m here, whatcha need?

[cyclopath]

[Soxhlet]

Did co2 tap out?

[cyclopath]

@Soxhlet

Did co2 tap out?

Nope!

[ravspd]

Quick chiller question!
So my polysci chiller is having issues maintaining temps. It can easily get down to -20 while i prepare it for my 2L roto. However, as i begin pulling vac and begin to recover etoh the chiller temp increases from -20 gradually back up to +15C or so. Is this a hardware issue? Can it be fixed in shop?
We are currently using denatured to condense but have switched heat transfer fluids frequently.

[ravspd]

@sidco

[square_root_pharms]

Did you read this yet?

@Beaker

Watts are simply an expression of work. Horsepower can be expressed in watts and as a matter of fact nearly every unit of energy of work can be expressed as watts. A watt is a unit of power defined as the rate of energy transferred per second.

What those wattage figures are trying to tell you is independent of what the serial number plate is telling you. The serial number plate usually near the inlet power tells you what to expect the machine to pull in either amps or watts as a unit running at full capacity in continuous operation. The plate never tells you peak amp draw nor does it tell you what mostly only electricians or engineers have heard of called “power factor”. In essence the data plate tells you how big your circuit breaker needs to be to keep from tripping and that is about it.

The chillers that publish their cooling capacity in watts/temps are telling you something very different. They are explaining that the ability to hold the base line temperature, expressed in watts, diminishes the colder you get. It gives the engineer a number to work from when designing that the data plate cannot. It means that if you want to hold the chiller at any given temp it will consume power just to hold the temp without anything external carrying heat into the coolant. In essence the wattage expressed at a temp is communicating to you how much heat energy the unit is capable of transfering and still maintain the set point temperature of the chiller itself.

Let’s say that your -40C rated chiller is set up correctly next to my -85C chiller. The rating tells us the maximum cooling (work) that the unit is capable of after the chiller itself has cooled to temp. Assume that we both have exactly identical set ups and we both want to run at -35C. At -35C your chiller will likely show very little wattage left over to actually cool the thing that is hot that needs cooling. Let’s say you have 10 watts of cooling power left at -35C. This means you can pump the equivelent of a ten watt light bulb of heat into the system every second and the chiller would hold temp but if you start pumping say 15 watts of heat through the unit then it will not hold temp.

My -85C chiller set at -35C might have 200 watts of cooling power left so I could pump the heat of a 200 watt light bulb through the system and still be able to hold -35C in this scenario with no problem. If more heat is applied than the unit can handle in watts for a given temp the unit simply does not get as cold. In fact, assuming your unit is working correctly, you could even predict how cold the unit will keep things by first knowing how much heat (work) will be run through the unit. Then an engineer can use the chart in reverse so to speak and predict the temperature the unit can hold and size a unit correctly for it.

The wattage on the data plate near the cord tells you how much amp draw on average to expect when the machine is drawing full current in normal operation. The wattage expressed in relation to the cooling potential tells you how much work will be left over to cool your process after the machine itself is cooled to the set point. Absolutely everything that allows heat to transfer into your process (like ambient air) adds heat and therefor takes away from the wattage you have left to chill the process.

[ravspd]

Thanks so much for your in depth response. I will give this some thought and hopefully be able to scale up soon.

[ravspd]

@Killbill

[Jay-TL]

Your chillers are way to close together. Also when was the last time you cleaned the filter? You should blast the filter with compressed air regualarly to maintain proper heat dissipation efficiency.

[Da_docta]

Iced tech?