_{m} = (Δt_{1} - Δt_{2})/ log_{e} (Δt_{1}/Δt_{2})

_{m} = log_{e} (Δt_{1}/Δt_{2})/ (Δt_{1} - Δt_{2})

_{m} = t_{m} = (Δt_{1} - Δt_{2}) log_{e} (Δt_{1}/Δt_{2})

_{m} = log_{e} (Δt_{1} - Δt_{2})/ Δt_{1}/Δt_{2}

**The automobile radiator is a heat exchanger of****Two long parallel surfaces each of emissivity 0.7 are maintained at different temperatures and accordingly…****The unit of Stefan Boltzmann constant is****Metals are good conductors of heat because****Wiens law states that the wave length corresponding to ________ is proportional to the absolute temperature.****Unit of thermal diffusivity is****The radiation emitted by a black body is known as****In case of liquids and gases, the heat transfer takes place according to****Fouling factor is used****Depending on the radiating properties, a body will be black when****The rate of heat flow through a body is Q = [kA (T₁ - T₂)]/x. The term x/kA is known as****In free convection heat transfer transition from laminar to turbulent flow is governed by the critical…****Thermal diffusivity is****In counter flow heat exchangers****The total radiation from a black body per second per unit area is ________ fourth power of the absolute…****Film coefficient is defined as the ratio of****Which of the following has maximum value of thermal conductivity?****The product of Reynolds number and Prandtl number is known as****A designer chooses the values of fluid flow rates and specific heats in such a manner that the heat…****The highest thermal diffusivity is of****Heat transfer takes place as per****The critical thickness of insulation for a sphere is****The ratio of surface convection resistance to the internal conduction resistance is known as****Reynolds number is the ratio of****Fourier's law of heat conduction gives the heat flow for****The natural convection air cooled condensers are used in****Total emissivity of polished silver compared to black body is****Film coefficient is defined as Inside diameter of tube****Thermal diffusivity of a substance is****Which of the following would lead to a reduction in thermal resistance?**