split across the evap

[jaybee]

Can anyone explain the information i could get from measuring the delta t across the evaporator and why? any replies are thanked in advance.

[nike123]

Can anyone explain the information i could get from measuring the delta t across the evaporator and why? any replies are thanked in advance.


http://www.refrigeration-engineer.com/forums/showthread.php?t=14830

[DEVITG]

Normally it is 10°C

If you can get the air flow , then you can have the Heat token by the evaporator by this formula

heat = flow * Air specific heat * delta T .

all it in consistent units .

[jaybee]

Can anyone explain the information i could get from measuring the delta t across the evaporator and why? any replies are thanked in advance.
i.e. if your evap delta t is to low what does this tells you as for as troubleshooting purposes? and if its too high? and can u explain your answer so i could understand how u arrived at your conclusion.

[Gary]

i.e. if your evap delta t is to low what does this tells you as for as troubleshooting purposes? and if its too high? and can u explain your answer so i could understand how u arrived at your conclusion.

Slower moving air through the evaporator loses more heat, therefore the air off temp is lower, therefore the delta-T (dT) is increased.

In other words, if the dT is too high, there is insufficient airflow through the coil.

(Assuming that the system is not capacity controlled)

Low dT is a less clear indicator. It could mean loss of capacity (for a wide variety of reasons)... or it could simply indicate high humidity in the refrigerated space.

[jaybee]

Slower moving air through the evaporator loses more heat, therefore the air off temp is lower, therefore the delta-T (dT) is increased.

In other words, if the dT is too high, there is insufficient airflow through the coil.

(Assuming that the system is not capacity controlled)

Low dT is a less clear indicator. It could mean loss of capacity (for a wide variety of reasons)... or it could simply indicate high humidity in the refrigerated space.
Thanks ,now it is more clear to me about high dt but a low dt is not as clear what will cause it .The air in almost same as out ??? thanks for replying

[Gary]

Thanks ,now it is more clear to me about high dt but a low dt is not as clear what will cause it .The air in almost same as out ??? thanks for replying

Now that you have determined that insufficient evap airflow is not the problem (low dT), the next step would be to check the condenser dT.

Slower moving air across the condenser will absorb more heat, thus the air out temp will be high, thus the cond dT will be high.

In other words, high cond dT (over 30F) indicates airflow problems.

And again, low dT is an unclear indicator.

Once we have determined that there is sufficient airflow through both coils (normal to low dT), we have narrowed down our search and can move on to refrigerant flow problems.