Brandon181
Mechanical
- Feb 16, 2012
- 12
A thermal engineer I work with designed a LPG Condenser Air Cooler and I have a few questions regarding the manufacturing of the unique design. The unit is 36' long with 6 passes/6 rows, Cstl, plug box header. The temperature inlet/outlet split are 500/109 F. There are two bays in parallel, each with 1 bundle. Most my questions are geared towards a multipass condenser, but some are ignorant Air Cooler questions in general.
First, I understand that in a multipass condenser with this extreme temperature differentials split headers will be required due to differing thermal expansions. It is my understanding that the mean metal temperatures will need to be evaluated from pass to pass to determine where the splits are required, for all operating scenarios.
1) Is there listed somewhere in literature a particular temperature differential between passes that will require you to use a split header for different materials? Or are designers required to calculate the thrust force of the thermal expansion vs the allowable stress on the tube to tubesheet joints?
2) In previous applications of a 2 pass condensing air cooler, we would always have the second pass sloped to allow for free draining of condensate. For the 6p/6r application, would all passes after the first need to be sloped? Or just the last pass? Or would the desinger need to determine in which pass enough condensate has formed to require free draining?
3) Would vents and drains be required on each split header? If so, where would they be located on the split header box?
4) What are thrust blocks and where would they be required? What is their function as related to the headers and side by side bays?
5) In a general case, if sloped passes are used, will they always slope to a split header? Is it more economical to have split headers than to have 1 oversized header box that would be large enough to contain the "flat" pass AND the sloped pass? (hope my wording of this quesiton was not too confusing)
I would appreciate any help!
First, I understand that in a multipass condenser with this extreme temperature differentials split headers will be required due to differing thermal expansions. It is my understanding that the mean metal temperatures will need to be evaluated from pass to pass to determine where the splits are required, for all operating scenarios.
1) Is there listed somewhere in literature a particular temperature differential between passes that will require you to use a split header for different materials? Or are designers required to calculate the thrust force of the thermal expansion vs the allowable stress on the tube to tubesheet joints?
2) In previous applications of a 2 pass condensing air cooler, we would always have the second pass sloped to allow for free draining of condensate. For the 6p/6r application, would all passes after the first need to be sloped? Or just the last pass? Or would the desinger need to determine in which pass enough condensate has formed to require free draining?
3) Would vents and drains be required on each split header? If so, where would they be located on the split header box?
4) What are thrust blocks and where would they be required? What is their function as related to the headers and side by side bays?
5) In a general case, if sloped passes are used, will they always slope to a split header? Is it more economical to have split headers than to have 1 oversized header box that would be large enough to contain the "flat" pass AND the sloped pass? (hope my wording of this quesiton was not too confusing)
I would appreciate any help!
