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Multiple Choic Questions. Please answer all. Thanks. e generally accepted value

ID: 2087684 • Letter: M

Question

Multiple Choic Questions. Please answer all. Thanks.
e generally accepted value of the critical Reynolds number for flat plate flow in forced convection is: 2000 2.7 The .2.3x10 5.0x10 23000 Many heat transfer correlations (especially in turbulent flow) are of the form: 2.8 Pr CRem Nu Re CNutm Pr St = C Rern Nun 2.9 The net heat flux leaving a surface is not found by: qnet"-qemitted" - Qabsorbed 2.10 Which of these is not an important parameter in the analysis of heat exchangers? Effectiveness, E .Unit-surface-conductance x Area, UA · Log Mean Temperature Difference, LMTD or ?? Number of Transfer Units, NTU . Heat Capacity Rate, C Effective Conductivity, Keff 2.11 The view factors (Fiy) around an enclosure, relative to a given surface, i, must sum to: 5.67x108 1.0 . the sum of the areas

Explanation / Answer

2.7) 5.0 x 105

2.8) Nu = C Rem Prn

2.9) Option D : qnet = G+ Eb.
As G represents incident radiation, it should be negative in sign and subtracted.

2.10) Effective Conductivity is not an important factor in analysis of heat exchangers

2.11) Sum of all view factors should be UNITY 1