All Free Chemical Engineering MCQs with Answers

• A. None of these
• B. Reheating furnace
• C. Glass tank furnace
• D. Cupola

Explanation: A cupola is charged intermittently with alternate layers of coke, metal and flux, so it is commonly classified as a batch furnace even…

• A. 50
• B. 100
• C. 150
• D. 250

Explanation: A chimney outlet temperature of about 150°C is a practical compromise: lower temperatures risk condensation and poor draught, while much…

• A. Rate of firing and emissivity of flame
• B. All A., B. and C.
• C. Nature of process; whether batch, continuous or intermittent
• D. Thermal conductivity of the charge & structural materials of furnace

Explanation: Charge heating and furnace losses are governed by firing rate and flame emissivity, material thermal conductivities, and whether the…

• A. To increase heat transfer by convection
• B. To ensure uniform temperature
• C. All A., B. and C.
• D. In furnaces, operating below 750°C

Explanation: Forced gas circulation increases convective heat transfer and reduces temperature differences within the furnace.

• A. Rotary hearth
• B. Shaft
• C. Tunnel
• D. Walking beam

Explanation: A walking-beam furnace advances stock by lifting and walking it forward, reducing contact losses and improving movement and fuel economy…

• A. CO
• B. All A., B. & C.
• C. High CO/CO2
• D. H2

Explanation: Scaling is oxidation of hot stock, so it is reduced by a reducing furnace atmosphere supplied by CO or H2; a high CO-to-CO2 ratio also…

• A. Temperature of flue gas
• B. All A., B. and C.
• C. Thickness of heating stock
• D. Thermal conductivity of stock

Explanation: Furnace capacity depends on the available heat in the flue gas, the stock's ability to conduct heat inward, and the distance heat must…

• A. 50 kcal/hr
• B. 200 BTU/hr
• C. 200 BTU/minute
• D. 200 BTU/day

Explanation: One ton of refrigeration equals 12,000 BTU per hour. Dividing by 60 gives 200 BTU per minute, so option C is the equivalent rate.

• A. Expansion valve
• B. Condenser
• C. Refrigerator
• D. Compressor

Explanation: Vapour-compression systems use a mechanical compressor, whereas absorption systems replace it with an absorber, pump, generator and…

• A. Prandtl number is one
• B. Schmidt number tends to infinity
• C. Nusselt number tends to infinity
• D. Archimedes number is greater than 10000

Explanation: When Prandtl number is one, momentum diffusivity and thermal diffusivity are equal.

• A. Heat conduction to viscosity of a fluid
• B. Cp/Cv of a fluid
• C. Elastic force to pressure force in the fluid flow
• D. Inertial force to elastic force in the fluid flow

Explanation: The Prandtl number is Pr = mu Cp/k, the ratio of momentum diffusivity to thermal diffusivity, so it compares viscous transport with heat…

• A. Density
• B. Specific heat
• C. None of these
• D. Thermal conductivity

Explanation: Thermal diffusivity is given by α = k/(ρCp), so it increases with thermal conductivity when density and specific heat are fixed.

• A. Heat flow rate
• B. Temperature difference
• C. Heat content in the system
• D. None of these

Explanation: In the thermal-electrical analogy, temperature difference corresponds to voltage and heat-flow rate corresponds to electrical current.

• A. 1 BTU/ft2.hr.°F/ft = 1.488 kcal/m2. hr.°C/m
• B. 1 BTU/ft2.hr.°F/inch = 1.488 kcal/m2. hr.°C/m
• C. 1 kcal/m.hr.°C = 0.672 BTU/ft.hr.°F = 1.163 W/m. °K
• D. 1 W/cm.°C = 85.985 kcal/m.hr.°C = 57.779 BTU/ft.hr.°F

Explanation: The first conversion is for conductivity units equivalent to BTU/(ft·hr·°F), giving 1.488 kcal/(m·hr·°C).

• A. 1 kcal/hr= 1.163 Watt
• B. 1 Watt = 1.163 kcal/hr
• C. 1 BTU/ft2.hr = 2.712 kcal/m2.hr
• D. 1 kcal/m2.hr = 0.3687 BTU/ft2.hr = 1.163 Watt/m2

Explanation: One watt equals approximately 0.8598 kcal/hr, so 1 kcal/hr equals 1.163 W, not the reverse.

• A. The minimum value of baffle spacing is 50 mm
• B. The maximum value of baffle spacing is equal to the I.D. of the shell
• C. The maximum unsupported tube span is generally about 75 times tube diameter, but is reduced to about 60 times for aluminium, copper & alloys of these
• D. Disk and doughnut baffle is the most commonly used baffle

Explanation: Segmental baffles are the usual choice in shell-and-tube exchangers, not disk-and-doughnut baffles.

• A. jH = (St)(Pr)2/3 = f/2
• B. jH = (St)(Pr)1/3 = f/2
• C. jH = (St)2/3(Pr) = f/2
• D. jH = (St)1/3(Pr) = f/2

Explanation: The Colburn analogy defines jH = St Pr^(2/3), and for the usual analogy it equals f/2.

• A. Nu = (Re) (Pr) (Gz)
• B. Nu = (Re) (Pr) (St)
• C. Nu = (Re) (Pr)
• D. Nu = (Pr) (St)

Explanation: The Stanton number is related to Nusselt number by St = Nu/(Re Pr), so rearranging gives Nu = Re Pr St.

• A. Lower economy
• B. Lower capacity
• C. Both A. & B.
• D. Higher economy

Explanation: In backward feeding, cold feed enters the last effect and is progressively heated as it moves toward the hotter effects, making better use…

• A. Backward
• B. Forward
• C. Parallel
• D. None of these

Explanation: Backward feeding places the most concentrated and viscous solution in the hottest effect, where its viscosity is lower and heat transfer…