Sub Zero Temperature Chamber (around -50°C.)

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Discussion Overview

The discussion centers around the design and implementation of a sub-zero temperature chamber capable of reaching around -50°C. Participants explore various cooling methods, suitable materials, and equipment for achieving and maintaining these low temperatures.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Experimental/applied

Main Points Raised

  • One participant suggests using liquid nitrogen for cooling but notes that it may not be suitable due to size limitations and the need for temperatures above -79°C.
  • Another participant proposes venting cold air from a liquid nitrogen dewar as a potentially easier and cheaper alternative to refrigeration, while cautioning about humidity and condensation issues.
  • Dry ice is mentioned as a cooling option, with a temperature of -79°C, which could be relevant for the chamber's requirements.
  • A participant shares their experience with Sun Electronics ovens that can achieve -50°C and below, recommending liquid CO2 systems for low temperatures and discussing the importance of temperature stability for testing protocols.
  • ThermoKing Super Freezer refrigeration units are highlighted as capable of maintaining -60°C, suggesting that suitable equipment for long-term refrigeration at -50°C should be available.
  • Quality Peltier thermoelectric cooling elements are mentioned as a possible solution, with varying effectiveness depending on the type and configuration used.
  • A humorous suggestion is made about using altitude to achieve lower temperatures, which may not be practical for the chamber's design.

Areas of Agreement / Disagreement

Participants present multiple competing views on the best approach to achieve the desired temperature, with no consensus on a single method or solution. Various cooling techniques and equipment are discussed, but the effectiveness and practicality of each remain uncertain.

Contextual Notes

Some participants note the importance of temperature stability and the thermal power that needs to be dissipated, but specific requirements and constraints are not fully defined. The discussion also reflects varying levels of expertise among participants, which may influence the proposed solutions.

Who May Find This Useful

This discussion may be useful for individuals involved in designing temperature-controlled environments, particularly in experimental or testing contexts within fields such as engineering and materials science.

TheEngineeringWay
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Hi Guys, Thanks for looking at the post firstly.

I'm in the process of creating a chamber roughly around 30mm x 50mm x 70mm (W, L, H). The chamber will be used below the typical refrigeration temperature (-18°) of around -50°C.

Please could you offer some advice where to start with this.

1. How can the cooling be achieved?
2. Any suitable pressure tight/ insulating chambers (e.g fridge)..what do you recommend?

I have looked at CPU cooling using liquid nitrogen, but temperatures are well below what I need it to be, and also, the sizes are quite limited..
 
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-50C is too warm for cryogenic cooling, as far as I know. If you can't use liquid nitrogen for whatever reason, then you will need some form of refrigeration. Alternatively, it may be easier to simply vent cold air from a liquid nitrogen dewar over whatever you wish to cool. This sort of convection cooling mechanism will probably be cheaper and easier to implement than refrigerating. Keep in mind that if the pressure of this flow is not sufficiently high, then humid room-temp air will drift in, and water will start to condense on whatever you are cooling and the air will warm the chamber. Hope this suggestion is helpful.
 
At my work we use Sun Electronics ovens to do temperature testing, which includes -50C and below:

http://www.sunelectronics.com/Temperature-Chamber-EC1X-Model.html

We use liquid CO2 systems to achieve the low temperatures and 10C/minute temperature ramps for reliability testing protocols, but I don't know if you can achieve -50C with slow refrigeration systems or not (I'm an EE, not an ME -- call Sun for technical advice).

How steady do you need to maintain your low temperature? If you need it to be steady to within a degree or two, you will need a good closed loop system like you get with commercial test ovens. If you don't need tight control, then maybe solid CO2 (as suggested by Russ) plus an arduino ventilation system might work.
 
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ThermoKing Super Freezer refrigeration units can keep a 40' container at -60C using a two stage refrigeration system. The first stage is a standard R-134a refrigerant reciprocating compressor. The second stage is a R-23 scroll compressor. You don't need anything that size but you should be able to find suitable equipment if you need long term continuous refrigeration at that temperature.

BoB
 
Welcome to PF.
You have not specified how much thermal power will need to dissipated.

Quality Peltier thermoelectric cooling elements can make a difference of 50°C in one module. Cheaper consumer Peltier cooling elements can operate easily with a 20°C temperature difference. If you place one or more Peltier cooler stages inside a conventional freezer it should meet your requirement.

Alternatively, use a balloon, aircraft or mountain to rise above 25,000 feet.
 

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