Mechanical Engineering - Heat Transfer, Refrigeration and Air Conditioning - Discussion


The by-pass factor for a cooling coil

[A]. increases with increase in velocity of air passing through it
[B]. decreases with increase in velocity of air passing through it
[C]. remains unchanged with increase in velocity of air passing through it
[D]. may increase or decrease with increase in velocity of air passing through it depending upon the condition of air entering

Answer: Option A


No answer description available for this question.

Nikhil Chaudhary said: (Jul 24, 2013)  
With increase in velocity temp. Decreases & bypass factor increases.

Sakti Prasad Dhar said: (Aug 3, 2013)  
Bypass factor is the (Amount of air bypassing the coil) divided by (the total amount of air passing the coil).

So a higher velocity of the passing air will decrease the time of contact for effective heat transfer and hence decrease the amount of heat transfer.

So it can be assumed that a greater portion of air is bypassing the coil without any heat transfer with the coil. So increasing the velocity of air decreases the Bypass factor.

Raju said: (Apr 15, 2014)  
As velocity increases Reynolds number increases which result in increase in heat transfer coefficient (turbulent) then bypass factor should increase?

Vicky said: (May 21, 2014)  
I'm totally agree with You (@Raju) with increase in velocity forced convection increase and with this the temperature decreases which should decrease the bypass factor.

Abhi said: (Mar 6, 2015)  
The by-pass factor can be increased by increasing the number of rows in a cooling coil or by decreasing the air velocity or by reducing the fin pitch.

Honey said: (Apr 17, 2015)  
Wrong buddy, by pass factor would reduced because time available low to make contact and enough heat will taken by air.

S K Pani said: (Jun 6, 2015)  
Let t1 = air before entering coil.

t2 = mean coil temperature.

t3 = air temperature cooling coil.

So bpf = (t1-t2)/(t3-t2).

So if the velocity of air will increase then the numerator will decrease which will result in a increase in bpf.

Vineet said: (Aug 5, 2015)  
By pass factor suggest the un-contacted air therefore if the speed will be high the air will not be able to contact the coil and hence bpf increases.

Shubh said: (Oct 30, 2016)  
Bypass factor is independent of velocity.

Golu said: (Jan 17, 2017)  
What is meaning of 'by pass air'?

Rajesh said: (May 17, 2017)  
Answer is correct.

Ysm said: (Jul 27, 2017)  
What is the significance of by-pass factor?

Ysm said: (Jul 27, 2017)  
The inefficiency of heating coil or cooling coil in not being able to heat or cool the incoming air to the temp of cooling coil. For proper design, bypass factor should be less.

Selvaraj said: (Sep 14, 2017)  
Anybody explain briefly about bypass factor.

Divyank Singh said: (Nov 21, 2017)  
According to nptel lecture 34 of rac. It has been said that as increasing velocity will reduce the time of contact so BPF decrease.

Harinder Singh said: (Aug 22, 2018)  
For the cooling coil, option A is correct.

For the heating coil, option B is correct.

Shrivardhan said: (Nov 28, 2019)  
In both cases, cooling and heating the Bypass Factor will increase.

Bhupendra Singh said: (Oct 28, 2020)  
By pass factor is the percentage of air travels through a coil without touching it so as velocity increases it do not have more time to be in contact with coil surface so percentage of air that is not in contact with coil surface increases means bypass factor increases.

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