Cooling Systems for Walk-in and Drive-in Environmental Test Chambers by Bemco Inc.

Walk-in Cooling Systems

Bemco Integral and Modular Walk-in and Drive-in Environmental rooms are available with a number of different cooling systems optimized for testing or processing conditions.

Some of the standard systems available are:

Cooling System	Low	Advantages	Disadvantages
Single Stage DX	-35 C	Utilities cost, reliable operation	Medium first cost, space required
Cascade DX (1)	-70 C	Utilities cost, lower temperatures	Higher first cost, space required
LN2 Heat Exchanger	-150 C	Very cold, air atmosphere (2)	Cost of LN2, too cold for RH use
LN2 Direct Injection	-180 C	Non oxidizing, lower first cost (2)	Cost of LN2, nitrogen in chamber
Fluid Chiller, Std. (5)(6)	-30 C	Uniformity in heat exchanger (3)	Higher first cost, maintenance
Fluid Chiller, Screw (5)(6)	-40 C	For greater than 200 hp (3)(4)	Highest first cost, maintenance

#	Note Text
1	DX = Direct Expansion inside the refrigeration cooling heat exchanger, recommended up to 100 hp per stage.
2	Can be combined with refrigeration systems to boost capacity or to extend low temperature operating range.
3	Greater than 200 hp heat exchangers require circulating fluid to evenly distribute the heat exchange medium.
4	Screw machine chillers are available with single stage refrigeration to -30 C and compound refrigeration to -40 C.
5	The most common chiller fluids Bemco recommends are Dowtherm J (-40 C) and Propylene Glycol (-20 C).
6	Additional information is available on our Bemco PCL Fluid Chiller System page on other fluid and circulating system options.

Single Stage DX:

Single stage refrigeration systems utilize hermetic or semi-hermetic, industrial grade mechanical refrigeration compressors running with modern, environmentally friendly refrigerants. These systems are either water or air condensed and include proportional process controls as well as automatic hot gas bypass and suction cooling unloading.

DX refers to direct expansion of the refrigerant in the heat exchanger coil.

Up to 100 horsepower, integral systems normally have the refrigeration systems mounted locally as part of the refrigeration package. Larger compressors and some prefabricated chambers are furnished with remote mounted systems in separate packages.

Cascade DX :

Bemco Cascade DX (direct expansion in the heat exchanger) cooling systems are similar to Single Stage DX except two refrigeration systems are provided. The first stage (the "High Stage" refrigeration system) condenses the second stage (the "Low Stage" refrigeration system) while the second stage cools the process - for instance the chamber air. An early article describing the principals of operation of this type of system is available here.

Both refrigeration stages use modern, environmentally friendly refrigerants. These systems can be either water or air condensed and include proportional process control as well as automatic hot gas bypass and suction cooling unloading. Cascade system low stages also have expansion tanks to maintain safe balance pressures. Bemco cascade systems are noted for their trailblazing reliability. Our exclusive high performance coaxial heat exchanger is used to efficiently transfer energy between the stages.

Cascade packages up to 60 x 60 horsepower, actually dual 30 x 30 systems, are locally mounted on both integral and prefabricated chambers. Above 60 x 60 horsepower, they are sometimes assembled in their own metal housing and furnished for installation by Bemco factory trained technicians on site.

Liquid Nitrogen:

Can be used for chamber cooling or boost cooling. Direct injection systems require the installation of a nitrogen gas sensing safety system by a Bemco approved vendor. Both direct liquid nitrogen injection and liquid nitrogen heat exchanger systems are offered.

Fluid Chiller:

Fluid chiller systems are recommended when the required cooling system becomes very large, when multiple heat exchangers are needed in the process, or when thermal shrouds or conductive baseplates are part of the process. They utilize industry standard circulating fluids to maintain chamber conditions. Bemco manufactures a large number of standard fluid chillers of various types. You can review our offering by going to our PCL Chiller Page by clicking here or our PAO Chiller Page by clicking here.

We also install commercial systems from other manufacturers. We recommend these systems when the required refrigeration capacity is at least 200 horsepower. The largest practically sized chiller packages are approximately 2,000 horsepower. Systems larger than 350 horsepower per compressor are ordinarily limited to "Single Stage DX" refrigeration systems utilizing "Screw Compressor" technology. Bemco recommended screw compressor chillers utilize rotary, oil injected, positive displacement screw compressors with automatic unloading.

Available Literature Includes:

Bemco FL Series Walkin Integral and Modular Rooms. Temperature, humidity and altitude, integrally constructed, and prefabricated walk-in environmental test equipment, drive-in room, and environmental test facilities from 6 feet by 6 feet by 7 feet to large building sized systems. Document is 8 pages, 674 KB download.

The systems described above are our Standard Models. We make custom equipment to your specifications. If you have any questions, need assistance in preparing a specification, or have a technical problem you want help with, we are ready. Our quotations and advice are free.