Chemical Engineering GATE 2025 Questions with Answer

Ques 40 Heat Transfer

Water flowing at 70 kg/min is heated from 25°C to 65°C in a counter-flow double pipe heat exchanger using hot oil. The oil enters at 110°C and exits at 65°C. If the overall heat transfer coefficient is 300 W/(m²K), the heat exchanger area is ______ m² (rounded off to 1 decimal place).
Specific heat of water and oil are 4.2 kJ/(kg°C) and 2 kJ/(kg°C), respectively.

Ques 41 Heat Transfer

Consider laminar flow of water over a wide flat plate maintained at a uniform temperature of 50°C as shown in the figure. The freestream velocity and temperature of water are 1.0 m/s (parallel to the plate) and 20°C, respectively. The distance x from the leading edge, at which the thermal boundary layer thickness δ_T=0.01 m, is ______ m (rounded off to 1 decimal place).

Ques 42 Heat Transfer

An electrical wire of 2 mm diameter and 5 m length is insulated with a plastic layer of thickness 2 mm and thermal conductivity k=0.1 W/(m K). It is exposed to ambient air at 30°C. For a current of 5 A, the potential drop across the wire is 2 V. The air-side heat transfer coefficient is 20 W/(m²K). Neglecting the thermal resistance of the wire, the steady state temperature at the wire-insulation interface is ______ °C (rounded off to 1 decimal place).

Ques 43 Instrumentation and Process Control

The vortex shedding meter is primarily used for measuring

Ques 44 Instrumentation and Process Control

Choose the transfer function that best fits the output response to a unit step input change shown in the figure

Ques 45 Instrumentation and Process Control

Consider a process with transfer function G_p=2e^-s/((5s+1)²)
A first-order plus dead time (FOPDT) model is to be fitted to the unit step process reaction curve (PRC) by applying the maximum slope method.
Let τ_m and θ_m denote the time constant and dead time, respectively, of the fitted FOPDT model. The value of τ_m/θ_m is ______ (rounded off to 2 decimal places).
GIVEN:
For G=1/(τs+1)², the unit step output response: y_(t)=1-(1+t/τ)e^-t/τ
dy(t)/dt = t/τ² e^-t/τ
d²y_(t)/dt² = 1/τ²(1-t/τ)e^-t/τ

Ques 46 Instrumentation and Process Control

The block diagram of a series cascade control system (with time in minutes) is shown in the figure.
For τ_I=8 min and K_c^s=1 the maximum value of K_c^m below which the cascade control system is stable, is ______ (rounded off to the nearest integer).

Ques 47 Mass Transfer

Schmidt number is defined as

Ques 48 Mass Transfer

If k is the mass transfer coefficient and D_v is the molecular diffusivity, which one of the following statements is NOT CORRECT with respect to mass transfer theories?

Ques 49 Mass Transfer

Which of the following statements regarding multiple effect evaporators is/are TRUE?

Ques 50 Mass Transfer

Oil is extracted from mustard seeds having 20 wt% oil and 80 wt% solids, using hexane as a solvent. After extraction, the hexane-free residual cake contains 1 wt% oil. Assuming negligible dissolution of cake in hexane, the percentage oil recovery in hexane is ______ % (rounded off to the nearest integer)

Ques 51 Mass Transfer

500 mg of a dry adsorbent is added to a beaker containing 100 mL solution of concentration 100 mg phenol/(L solution). The adsorbent is separated out after 5 h of rigorous mixing. If the residual concentration in the solution after separating the adsorbent is 30 mg phenol/(L solution), the amount of phenol adsorbed (in mg per gram of dry adsorbent) is

Ques 52 Mass Transfer

Consider moist air with absolute humidity of 0.02 (kg moisture)/(kg dry air) at 1 bar pressure. The vapour pressure of water is given by the equation
ln P^sat = 12-4000/(T-40)
where P^sat is in bar and T is in K. The molecular weight of water and dry air are 18 kg/kmol and 29 kg/kmol respectively. The dew temperature of the moist air is ______ °C (rounded off to the nearest integer).