Chemical Engineering Answers

Sulphur dioxide is to be scrubbed from an air stream in a small packed tower by contacting it with an organic amine. The feed gas 3% SO2, by volume, and 95% of it is to be absorbed. The total gas rate is 150 m^{3}/h. at 20^{°}C and 1.1 bar absolute pressure. The liquid enters the column at rate of 1.40 kmol / h. Give:the overall mass transfer coefficient, KG=3.2*10^{-4} kmol/m^{2}.s. bar; the effective gas-liquid contact area =105 m^{2} per m^{3} of packed volume; slope of the equilibrium line, m=0.17 . Determine the number of overall gas-phase mass transfer units and the packed height if the column is 1 ft in diameter.

A metal ball (radius 2.5 cm) initially at a uniform temperature of 450°C is suddenly placed in a controlled environment in which the temperature is maintained at 100°C. The convective heat transfer coefficient is 10 W/(m² -K). Determine the time taken (in hours) for the metal ball to cool to 150 °C ? Clearly mention the suitable assumptions if necessary?. Property data are given below.

Property of all metal ball,unit ___________ value

Density, kg/m³_______7800

Thermal conductivity,W(m-°C)____35 

Heat capacity, (J/kg-°C) 460

A composite wall is formed of a 2.5 cm copper plate (k=385 W/m-K). a 3.2 cm layer of

asbestos (k=0.2 W/m-K), and a 5 cm layer of fibreglass (k=0.045 W/m-K). The wall is subjected to an overall temperature drop of 560°C. Calculate the heat flux through the composite wall and also determine the temperature drop across the asbestos layer?

A schedule number 40 standard steel pipe (outer diameter 4.5 in. and wall thickness 0.237 in.) carrying steam is lagged (insulated) with two layers. First layer (near the steel pipe) having 50mm thickness is made of 85% magnesia and second layer having 60 mm thickness is made of cork. The inner surface temperature of the steel pipe is maintained at 150°C and the outer surface temperature of the cork is maintained at 35°C. Determine the individual thermal resistance of each layer and the rate of heat loss per meter length of the pipe. Consider only the conduction heat transfer. Make suitable assumptions if necessary? (Take

1 in.= 2.54 cm)

Material: Thermal.conduct.     

Steel pipe.   45(W/(m-°C) 

85% magnesia. 0.07 "

Cork      0.043 "

A metal ball (radius 2.5 cm) initially at a uniform temperature of 450°C is suddenly placed in a controlled environment in which the temperature is maintained at 100°C. The convective heat transfer coefficient is 10 W/(m² -K). Determine the time taken (in hours) for the metal ball to cool to 150 °C ? Clearly mention the suitable assumptions if necessary?. Property data are given below.

Property of all metal ball,unit ___________ value

Density, kg/m³_______7800

Thermal conductivity,W(m-°C)____35 

Heat capacity, (J/kg-°C) 460

A light fuel oil is used in the tube side of a 2-4 shell-and-tube heat exchanger. Water is heated in the shell side from 10°C to 50°C while the oil is cooled from 90°C to 60°C. The overall heat-transfer coefficient is 53 W/(m²-°C). The LMTD correction factor is 0.975.

Calculate the area of the heat exchanger for a total heat transfer rate of 500 kW. ?

Draw the temperature profiles of hot and cold fluids in a 1-2 shell and tube heat exchanger?

Draw the neat sketch of a 1-2 shell and tube heat exchanger?

Determine all the view factor for a duct of equilateral triangular cross section. Assume that all surfaces are plane.?

A chamber for heat curing large aluminium sheets, lacquered black on both sides, operates by passing the sheets vertically between two steel plates 150mm apart. One of the steel plates is at 300°C and the other plate is at 25°C. The emissivity of steel plates is 0.56 and the Stefan-Boltzmann constant is 5.67x108 W/(m²-K4). What is the heat transfer rate per unit area between the plates?