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Friobernal
01-01-2003, 08:16 PM
Hi all,

Reading a book i have found the next:

"Unfortunately, there has to be a throttling in a valve in the UC leg, which takes the larger part of the flow."

This part is talking about pressure drop and, because of my bad english, i donīt understand what "throttling in a valve" means. The translation of throttling in spanish has no sense at all.

Can anybody explain it to me in another words?

Regards

Andy
01-01-2003, 08:35 PM
Hi, friobernal:)
throttling in a valve is simply closing it in to decrease flow (not fully). This maybe a hand regulating valve for liquid flow control, or even an expansion valve, realy depends on the context.

Hope this helps, Regards. Andy.

bhrobin
03-01-2003, 07:11 AM
I was thinking that if Andy's reply still does not work for you, I might have a go at it. It might be helpful if you could give us a bit more of the surrounding text as a context. (mas o menos)

- Bruce in Kansas:confused:

Friobernal
03-01-2003, 07:06 PM
Hi, bhrobin (and AndyHer;)

Here is the context:

The total pressure drop in the loop (42.8 (HT Evaporator PHE) + 38.5 kPa (LT condenser BHE) is now smaller than the permissible. Unfortunately, there has to be a throttling in a valve in the UC (Unit Cooler) leg, which takes the larger part of the flow. Fortunately the LT condenser overdimensioned. Thus by allocating less liquid to this leg both the margin and the DP will decrease. If the overall flow also increases, the available head will decrease but the MTDs will increase.

The pressure drop in the UC 19 kPa

*Weīve got 30 % P-glycol (UC)
*R410a in LT condenser
*NH3 in HT evaprator

Thatīs what iīve got. Can anybody translate it to me:D ?

Regards and Happy new year

bhrobin
04-01-2003, 07:42 AM
Friobernal -

Well, my friend, it is not your English that is the problem. The original text was surely written in something else and translated very poorly into English. I've seen computers do a better job than that.

I haven't any experience with Ammonia systems, and it seems to me this may be a cascade system. I want to help but not mislead you. But, I will try. Here goes:

The total pressure drop in the loop (42.8 (HT Evaporator PHE) + 38.5 kPa (LT condenser BHE) is now smaller than the permissible. Unfortunately, there has to be a throttling in a valve in the UC (Unit Cooler) leg, which takes the larger part of the flow.

The difference in pressure between the incoming and the outgoing refrigerant in the loop with the HT evaporator and the LT conenser is now less than ideal. This is because a valve in the unit cooler circuit has opened and the flow through this part of the loop has increased. Throttling in this case refers to more or less flow through some kind of controlling device or valve.

I have formed a picture in my mind of a loop with two heat exchangers in series in one loop and a unit cooler in an adjacent, parallel loop.

Fortunately the LT condenser overdimensioned. Thus by allocating less liquid to this leg both the margin and the DP will decrease. If the overall flow also increases, the available head will decrease but the MTDs will increase.

:) The low temperature condenser is somewhat larger than necessary so that when refrigerant flow in the circuit is reduced there is still enough condensing capacity, even as the pressure drop decreases. On the other hand, when normal (increased) flow is resumed, head pressure will decrease.

The pressure drop in the UC 19 kPa

*Weīve got 30 % P-glycol (UC)
*R410a in LT condenser
*NH3 in HT evaprator