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

4. 

In free convection heat transfer transition from laminar to turbulent flow is governed by the critical value of the

[A]. Reynold's number
[B]. Grashoff's number
[C]. Reynold's number, Grashoff's number
[D]. Prandtl number, Grashoff's number

Answer: Option D

Explanation:

No answer description available for this question.

Sai Rama Prabhakar said: (Jun 7, 2013)  
In free convection the two dimensionless numbers are grashof's number & prandtl number where it is replaced by reynold's number & prandtl number for forced convection.

Sanju said: (Nov 11, 2013)  
In free convection h is function of Pr number and Gr number.

In forced convection h is function of Pr number and Re number.

Sudheer said: (Jun 23, 2015)  
In free convection the two dimensionless numbers are Grashof's number & Prandtl numberwhere it is replaced by Reynold's number & Prandtl number for forced convection. In free convection h is function of Pr number and Gr number.

Prandtl number, Grashoff's number. In forced convection h is function of Pr number and Re number.

Sai Krishna said: (Jul 15, 2015)  
Would you please explain me Reynold's number, Grashof's number and Prandtl number?

Rohit said: (Oct 1, 2015)  
Reynolds number = Re = Inertia forces/Viscous forces.

Re = VD/v or (rho*V*D)/mu.

Prandtl number = hl/k.

Grashoff's number = (rho*g*B*l2*dt3)/mu.

Ayyappa said: (Oct 27, 2015)  
In free convection Reynold's number matters. It is simply function of Grashoff's and prandtl.

Amulraj said: (Apr 2, 2016)  
Refer heat and mass transfer data book CP Kothandraman. It contains all the formulas and relations.

Gaurav said: (Dec 16, 2017)  
Critical value in free convection is Grashoff number only.
Nusselt number is a function of GR No and PR No.
So the answer should be B.

Sreerag said: (Dec 24, 2017)  
@Rohit.

I think Prandtl no = meu. Cp/k.

Jonty said: (Aug 6, 2018)  
In free convection Nusselt number is a function of Re and Gr, on the other hand it is a function of Re and Pr for forced convection. So, answer C is correct.

Kadam Vishal said: (Oct 8, 2018)  
According to me, Option A is also correct.

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