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angryk
16-01-2003, 02:43 AM
While taking a break at the job I was at, I decided to have a look at the rest of their equipment. While in the walk-in refrigerator, I noticed the tev bulb is in the vertical position on a horizontal pipe. Upon closer inspection I discovered that it is in a type of immersion well. Half the bulb was inside the suction line, while the top half was exposed. I am assuming that the nut around the bulb is some sort of compression fitting or somethig similar. The box was down to temperature and no obvious problems were apparent. Seeing that It was not what I was there for and the customer was'nt complaining, I left it alone. But that still leaves me with the question of what kind of setup it is and is it correct?:confused: I would think that if the bulb itself is in the actual refrigerant flow, that it shold be doing it's job. That is as long as the exposed part is properly insulated.

Prof Sporlan
17-01-2003, 05:44 AM
You may have been looking at a Bohnmizer coil which uses TEV of Sporlan manufacture, and its sensing bulb is often in a bulb well. The well is normally a copper tube or fitting positioned and brazed perpendicular to the suction line, and honed to the correct ID to fit the TEV's sensing bulb. As a result, the bulb is not directly in the refrigerant flow, but it is in an environment to better sense refrigerant vapor temperature. If the Prof is remembering correctly, this is the case with the Bohnmizer coil.

There is some merit placing the TEV's sensing bulb in a well on a refrigeration coil, but many find the aggravation necessary to make the well correctly isn't worth the added benefits.

angryk
18-01-2003, 12:25 AM
Thanks professor, good to know.:)

John K.

Michael Bellstedt
20-01-2003, 10:42 PM
I might add that I have applied this technique in the past whereever I required maximum sensitivity and reaction time from the TX valve, eg. where liquid carryover to the compressor during transient operation might occur. With the bulb within the suction line, the heat transfer to the bulb is far more effective, so the bulb will react far more quickly to any changes in suction conditions. For normal constant temperature applications (eg. coolrooms), this is rarely needed and hence not worth the effort, but if you are designing eg. a variable temperature and variable heat load climatic test chamber, this can help.

cheers

Michael Bellstedt

Minus40
Sydney