# Heat Transfer Homework

Visit Stack Exchange I have huge vessel filled with \$CH_4\$ and another vessel filled with hydrogen. Assuming the heat transfer coefficients are same, the \$CH_4\$ would cool faster compared to the hydrogen vessel, this is because the hydrogen vessel has larger heat content and takes more time cool to ambient. Yes, it takes more energy (heat is a type of energy) to heat up the substance with the greater heat capacity, all other things (such as \$\Delta T\$, and mass) being equal.Lets assume they have the same mass of gas say kg\$. Since the heat capacity of hydrogen is greater than that of \$CH_4\$ (for \$H_2\$ it is KJ/kg-K\$ and for \$CH_4\$ it is .889KJ/kg-k\$), the amount of heat absorbed to raise the temperature of hydrogen is greater than \$CH_4\$ This is because \$Q=m C_P\Delta T\$ and m and \$\Delta T\$ are same for both \$H_2\$ and \$CH_4\$, \$C_P\$ is higher for hydrogen. If both substances have the same heat transfer coefficient (measured in units of power per unit temperature per unit area), then the one with the greater heat capacity will cool down more slowly, all other things (critically geometry of container) being equal.

Visit Stack Exchange I have huge vessel filled with \$CH_4\$ and another vessel filled with hydrogen. Assuming the heat transfer coefficients are same, the \$CH_4\$ would cool faster compared to the hydrogen vessel, this is because the hydrogen vessel has larger heat content and takes more time cool to ambient. Yes, it takes more energy (heat is a type of energy) to heat up the substance with the greater heat capacity, all other things (such as \$\Delta T\$, and mass) being equal.Lets assume they have the same mass of gas say kg\$. Since the heat capacity of hydrogen is greater than that of \$CH_4\$ (for \$H_2\$ it is KJ/kg-K\$ and for \$CH_4\$ it is .889KJ/kg-k\$), the amount of heat absorbed to raise the temperature of hydrogen is greater than \$CH_4\$ This is because \$Q=m C_P\Delta T\$ and m and \$\Delta T\$ are same for both \$H_2\$ and \$CH_4\$, \$C_P\$ is higher for hydrogen. If both substances have the same heat transfer coefficient (measured in units of power per unit temperature per unit area), then the one with the greater heat capacity will cool down more slowly, all other things (critically geometry of container) being equal.

FIND: (a) Equivalent thermal circuit, (b) Expression for heater temperature, (c) Ratio of outer and inner heat flows and conditions for which ratio is minimized.

ASSUMPTIONS: (1) One-dimensional, steady-state conduction, (2) Constant properties, (3) Isothermal heater, (4) Negligible contact resistance(s).

Convective coefficients on the inside and outside surfaces of a window are 20 W/m 2 - K and 15 W/m 2 - K, respectively.

What temperature drop will exist across each of the glass panes?

What will be the average temperature of the air between the glass panes? Ts =° 100 c Tcsurrounding= 25 ° Air space 0.8cm wide Window glass--0.32 cm thick Solution: q R Ri − ==× − ==× 3 0 − ==× q W ∑R Air space 0.8cm wide 250k hi 295k h 0 Window glass 0.32 cm thick Ti To Ri RGL RAS RGL Ro KNOWN: Hot water pipe covered with thick layer of insulation.