RE: Splitting Flow Equally

There is a rule of thumb used to insure equal flow across two or more devices along a common header.

Make the cross sectional area of the header equal or greater than the sum of each device inlet area. this insures that the majority of the pressure drop occurs across each device, and little pressure drop occurs across the header system. this helps balance flow.

At 11:34 PM 11/16/2002 +1300, you wrote:
>Dear Ahmed Vawda
>
>You do not need to worry too much as the system you describe is self
>balancing on the syrup side assuming a "clean" syrup, and a generous supply
>of low viscosity cooling medium. Consider this: If one HE (heat exchanger)
>is cooling more than the other then the product viscosity, and therefore the
>pressure drop will increase. This means the syrup flow will seek the hotter
>HE. As the flow through the hotter HE increases, the heat transfer
>coefficient will increase and cooling will be increased. By regulating the
>cooling fluid flow according to exit temperature, it will be easy to keep
>the system balanced. If you take care in arranging the inlet and outlet
>pipework for both fluid streams to have equal resistance, then I doubt that
>you would need any form of automatic control. Remember that each HE, I
>assume (plate or through tube), has a series of parallel flow channels. By
>having two HE units, you are merely doubling the number of parallel paths.
>Allow for thermometers plus a regulating valve on the outlet stream of each
>HE plus careful pipework to give both HEs equal flow. If the price of the
>extra equipment still favours the two HEs then I would say go with it.
>
>Cheers
>
>Steve McKenzie
>
>-----Original Message-----
>From: Ahmed Vawda [mailto:avawda@aksugar.co.ae]
>Sent: Saturday, November 16, 2002 10:32 PM
>To: 'PipingDesign@yahoogroups.com'
>Subject: [PipingDesign] Splitting Flow Equally
>
>
>Dear Forum Members
>
>I am planning to buy a heat exchanger to cool hot syrup. The problem is that
>the price of two smaller units is cheaper than the price of one large unit.
>Besides the price, the pressure drop in the large unit is greater than that
>in the two smaller units. How can I distribute the flow equally, without the
>use of expensive flow measurement devices?
>
>
>Ahmed Vawda
>Process Engineer
>Al Khaleej Sugar Dubai
>
>
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>
>
>
>Discussion List sponsor: Texas Flange - a good source for information on
>industrial flanges, all they ask is for referrals for designs they help with.
>877-610-8924.
>www.texasflange.com
>=====================================================
>unsubscribe: PipingDesign-unsubscribe@yahoogroups.com
>=====================================================
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Thomas G Laupa PE
Senior Engineer - Ondeo Nalco Applied Services Office Address: 1001 Frontenac Rd, Naperville, IL, 60566 Courier Address: 1003 Remington, Fort Collins, CO, 80524 800-944-6252 x5745
800-493-5009 fax Received on Sat Nov 16 12:18:00 2002