Quiz Seven Flashcards
How is Reynolds number calculated?
Re=(diametervelocitydensity)/viscosity
What is Nussult number? How is it calculated?
Nussult number is the ratio of conduction resistance to convective resistance. Nu = (convective heat transfer coefficient*diameter of heat exchanger)/thermal conductivity
What is Prandtl number? How is it calculated?
Prandtl number is the ratio of kinematic viscosity to thermal diffusivity. Pr = (specific heat*viscosity)/thermal conductivity
How can Nussult number be calculated using Reynolds number and Prandtl number?
Nu = constantReynolds number^mPrandtl number^n
How is Nussult number calculated during forced convection in laminar flow?
Nu = 1.86(RePr(diameter/length))^0.33(viscosity bulk T/viscosity wall T)^0.14
How is Nussult number calculated during forced convection in turbulent flow?
Nu = 0.023Re^0.8Pr^0.33*(viscosity bulk T/viscosity wall T)^0.14
What is natural convection?
Natural convection is convective heat transfer with no external force
What is Grashoff’s number?
Grashoff’s number is the ratio of buoyancy forces to viscous forces
What is Rayleigh’s number?
Rayleigh’s number is Grashoff’s number multiplied by Prandtl’s number
What are the two type of heat exchangers? Give examples of both.
Two types of heat exchangers are contact and non-contact. Contact heat exchangers are steam infusion and steam injection. Non-contact heat exchangers are plate, tubular, triple tube, shell and tube, and scraped surface heat exchangers.
What is regeneration?
Regeneration is using the already heated medium to heat the cold medium and to use the cold medium to bring down the temperature of the heated medium
How is log mean temperature calculated?
LMT = (change in temperature of 1 - change in temperature of 2)/natural log(change of temperature of 1/change of temperature of 2)
What are some factors affecting heat transfer?
Some factors that affect heat transfer are flow rate, physical properties, thermal properties, area of heat exchanger, and temperature difference between products
