Liquid helium and liquid nitrogen are both used as coolants; He(e) boils at 4.21 K, and N2(e) boils at 77.35 K. The specific heat of liquid helium near its boiling point is 4.25 J K-1g-1, and the specific heat of liquid nitrogen nearits boiling point is 1.95 J K-1g-1. The enthalpy of vaporization of He(e) is 25.1 J g-1, and the enthalpy of vaporization of N2(e) is 200.3 J g-1(these data are calculated from the values in Appendix F). Discuss which liquid is thebetter coolant (on a per-gram basis) near its boiling point and which is better at its boiling point.

In a process plant handling benzene compounds, a vertical thermosyphon reboiler is used in a column distilling crude benzene at 1 bar. Steam is available at 20 bar with the column bottom pressure 1.2 bar. Boiling point of benzene is 180 °C at a pressure of 1.2 bar. Molecular weight of benzene is 78 kg/kmol. Critical temperature of benzene is 652 K. Latent heat of vaporization is 39,000 kJ/kmol. Saturation temperature of steam is 215 °C. Heat load is 700 kW and heat flux is 28,000 W/m2. Reboiler Configuration: Tubes are 25 m.m O.D and 20 m.m I.D of 2 m long with triangular pitch arrangement. Determine the following design parameters: i. Area required for reboiler & amount of vaporization per hour ii. Shell inside diameter with shell clearance of 34 m.m and number of tube passes =2. iii. Outlet pipe diameter of outlet pipe and state the assumption

1. A food product containing 82% moisture content is being frozen. Estimated specific heat of the product at -6 ° C when 75% of the air is frozen. The specific heat of the dry product is 2 kJ / (kg ° C). it is assumed that the specific heat of water at -10 ° C is the same as that of water at 0 ° C, and the specific heat of ice follows the function Cp ice = 0.0062 T frozen + 2.0649.    Cp of frozen product = Answer kJ / kg ° C

The vapor pressure of liquid cadmium is 400 mm Hg at 983 K. Assuming that its molar heat of vaporization is constant at 100 kJ/mol, the vapor pressure of liquid Cd is mm Hg at a temperature of 959 K.