It is good piping design ?

[oilzee]

Hello every body , i have a question have not been solved, i hope i will get the answer in this forum .my boss always design the refrigeration piping by putting the suction line and discharge line together ( two copper pipe touch each other ) with pipe insulation .Is this good for the evaporator superheat adjustment ? i read a lot of forum stated that good design has no need to adjust the TXV but if i am not adjust the TXV i will get high superheat at the compressor .( Example : piping for blast freezer ,120 feet long ).thanks for help !

[nike123]

Some compressor manufacturers want superheat of 20K or more in low temperature applications. If we adjust that with TEV than evaporator will be inefficient. Therefore, it could be good to have some form of suction gas heat exchanger like in case when two pipes are together. You have better subcooling and better superheat in such case. Sometimes when that could not be achieved with pipes, you should install separate suction gas heat exchanger.
But if you have application as in air conditioning then such a superheat is bad for compressor then you should laid these pipes separately isolated.

[oilzee]

thanks for reply , i think i got the answer here .Beside that should i increase the superheat at the compressor to make the maximum capacity at the evaporator ?

[nike123]

thanks for reply , i think i got the answer here .Beside that should i increase the superheat at the compressor to make the maximum capacity at the evaporator ?

Maximum capacity at evaporator is when superheat is 0K!
You must maintain superheat at reasonably high level at which you are sure that there is no danger of liquid flood back to compressor in all working conditions, and at same time, low as possible to utilize evaporator surface as much as possible.

Check this!

[oilzee]

got it , i am going to do the observation before made any adjustment for that system . thanks

[US Iceman]

...[FONT=Verdana]by putting the suction line and discharge line together

I hope you mean the liquid line and NOT the discharge line.

The TXV controls the superheat of the evaporator. If you add heat to the suction vapor, The vapor temperature will increase. This results in a higher SUCTION superheat at the compressor. This can cause the compressor to overheat, which you do not want.

oilzee]
( Example : piping for blast freezer ,120 feet long )

That is a perfect example of where not to connect the liquid and suction lines. If you want subcooling use a separate mechanical subcooler, not the suciotn line.

[oilzee]

I hope you mean the liquid line and NOT the discharge line.

First of all ,thanks for adding another infomation .It is liquid line not discharge line .That is why we always get high superheat at compressor . i hope my boss will accept these all infomation .