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GATE Food Plant Design, Hygienic Engineering, Utilities & Automation: practice questions

GATE — Engineering Sciences (XE), Section G Food Technology · India · IITs and IISc on rotation (2026: IIT Guwahati)

Original practice questions written to the published syllabus · not past papers
10worked here, free
20written to this exam in this subject
2syllabus units

About GATE

GATE — Engineering Sciences (XE), Section G Food Technology is a postgraduate admission exam run by IITs and IISc on rotation (2026: IIT Guwahati), for candidates in India. Computer-based, 3 hours, 100 marks. MCQ, MSQ and NAT. General Aptitude is common to every GATE paper; within XE, Section A Engineering Mathematics is compulsory (stated on the 2026 XE-A syllabus) and the candidate chooses two further sections, of which G Food Technology is one. The split of marks between GA, XE-A and the two chosen sections is from Laisha's knowledge of earlier brochures and was not re-read for 2026.

Source: gate2026.iitg.ac.in.

Checked against the exam body's published information. Formats and fees change; confirm the current edition there before you book.

Food Plant Design, Hygienic Engineering, Utilities & Automation in GATE

Turning a process into a plant that is hygienic, efficient and safe: hygienic equipment and building design, plant layout, process flow and equipment selection, steam, water, compressed air and refrigeration utilities, instrumentation and automation, energy audit and scale-up. Agricultural Engineering's food-quality-safety-plant-design covers plant location, layout and feasibility reports; this subject adds hygienic engineering (EHEDG and 3-A principles), utilities, automation and energy management in depth.

Our 20 GATE questions in this subject: 7 easy, 8 medium, 5 hard, across 2 units.

10 practice questions, worked

Choose an answer, then open the working. Each explanation says why the right answer is right and why the others are not.

These 10 were written to GATE and are not shown on any other exam's page.

Question 1 · hard

Feedwater contains 200 mg/L dissolved solids and boiler water must be kept at or below 2,500 mg/L. The boiler produces 4,000 kg/h of steam (assume pure). What blowdown flow is needed?

  1. 348 kg/h
  2. 320 kg/h
  3. 32 kg/h
  4. 50,000 kg/h
Answer and working

A. 348 kg/h

Blowdown as a fraction of feedwater = 200 ÷ 2,500 = 0.08. Feedwater F = steam + blowdown, and blowdown = 0.08F, so F = 4,000 ÷ 0.92 = 4348 kg/h and blowdown = 348 kg/h. Taking 8 % of the steam instead of the feedwater gives 320 kg/h, a common slip.

Question 2 · easy

What is the main purpose of a deaerator in a boiler feedwater system?

  1. Remove calcium and magnesium hardness that forms scale
  2. Remove dissolved O2 and CO2, which cause corrosion
  3. Add air to the feedwater to improve combustion
  4. Cool the condensate before it returns to the boiler
Answer and working

B. Remove dissolved O2 and CO2, which cause corrosion

Heating feedwater in a deaerator drives off O2 and CO2, the main corrosion agents; oxygen scavengers remove the remainder. Hardness is removed by softening; combustion air is supplied separately; condensate is returned hot to save fuel.

Question 3 · hard

Condensate at 10 bar absolute (saturated liquid enthalpy 762.8 kJ/kg) is discharged to a vessel at atmospheric pressure (saturated liquid enthalpy 419.0 kJ/kg, latent heat 2,257 kJ/kg). What fraction flashes to steam?

  1. 18.6 %
  2. 33.8 %
  3. 15.2 %
  4. 45.1 %
Answer and working

C. 15.2 %

Flash fraction = (h_f at high pressure − h_f at low pressure) ÷ h_fg at low pressure = (762.8 − 419.0) ÷ 2,257 = 0.152, about 15.2 %. Dividing by the high-pressure liquid enthalpy gives 45.1 %, a wrong basis. This flash steam can be recovered for low-pressure heating.

Question 4 · hard

A steam main must carry 2,000 kg/h of saturated steam with a specific volume of 0.194 m³/kg at a design velocity of 25 m/s. What internal diameter is needed?

  1. 66 mm
  2. 148 mm
  3. 37 mm
  4. 74 mm
Answer and working

D. 74 mm

Volume flow = 2,000 × 0.194 ÷ 3,600 = 0.1078 m³/s; area = 0.1078 ÷ 25 = 0.00431 m²; D = √(4A/π) = 0.074 m ≈ 74 mm. Taking √A treats the pipe as square (66 mm); 37 mm and 148 mm confuse radius and diameter. A larger diameter is chosen if pressure drop over the run is too high.

Question 5 · easy

Why is returning condensate to the boiler house worthwhile?

  1. Food law requires all condensate to be returned regardless of its condition
  2. It is hot, already treated water, so it saves fuel, water and treatment chemicals
  3. Condensate is colder than fresh water, which improves the boiler's draught
  4. It contains dissolved salts that help keep boiler water alkalinity in range
Answer and working

B. It is hot, already treated water, so it saves fuel, water and treatment chemicals

Condensate carries sensible heat and has already been softened and treated, so returning it cuts fuel, make-up water and chemical use. It is hot and low in dissolved solids; contaminated condensate must be rejected, not returned.

Question 6 · medium

Why do oil-free compressors not remove the need for filtration of food-contact compressed air?

  1. Oil-free compressors add lubricating oil downstream of the air end
  2. Filters are needed only to reduce compressor noise in the plant
  3. Oil-free air is too dry and must be humidified before use
  4. Intake air already carries hydrocarbons, particles and moisture
Answer and working

D. Intake air already carries hydrocarbons, particles and moisture

Oil-free machines avoid adding compressor oil, but ambient air contains hydrocarbon vapour, dust and water, so dryers and coalescing, carbon and sterile filters are still used for contact applications. The other statements are false.

Question 7 · medium

A compressor draws 100 kW and runs 8,000 hours a year; a survey finds that leaks account for 10 % of its output. Electricity costs 0.12 currency units per kWh. What is the annual cost of the leaks?

  1. 96,000 currency units
  2. 960 currency units
  3. 1,200 currency units
  4. 9,600 currency units
Answer and working

D. 9,600 currency units

Leak power ≈ 10 % × 100 kW = 10 kW; energy = 10 × 8,000 = 80,000 kWh; cost = 80,000 × 0.12 = 9,600. 96,000 is the cost of the whole compressor, 960 drops a factor of ten, and 1,200 omits the hours.

Question 8 · medium

A vapour-compression system delivers 210 kW of cooling with a compressor power input of 60 kW. What are its COP and the heat rejected at the condenser?

  1. COP 3.5; condenser 270 kW
  2. COP 3.5; condenser 150 kW
  3. COP 4.5; condenser 210 kW
  4. COP 0.29; condenser 150 kW
Answer and working

A. COP 3.5; condenser 270 kW

COP = cooling ÷ work = 210 ÷ 60 = 3.5. By energy balance the condenser rejects the evaporator load plus compressor work: 210 + 60 = 270 kW. Subtracting the work (150 kW) reverses the balance; 0.29 inverts COP; 4.5 is the heating COP of a heat pump.

Question 9 · easy

Why is ammonia (R717) widely used in large food-plant refrigeration despite its toxicity?

  1. It is non-toxic in the concentrations reached during any credible leak
  2. It is efficient and cheap and has zero ozone-depletion and global-warming potential
  3. It is the only refrigerant that can reach freezing temperatures below −20 °C
  4. It is not flammable at any concentration, so machinery rooms need no ventilation or detection
Answer and working

B. It is efficient and cheap and has zero ozone-depletion and global-warming potential

Ammonia is thermodynamically efficient, inexpensive and has no ODP or GWP, but it is toxic and flammable within a range, so it needs ventilated machinery rooms, leak detection, low charges and trained staff. Other refrigerants, including CO2 and HFCs, also reach freezing temperatures.

Question 10 · medium

Under which international agreement are high-GWP HFC refrigerants being phased down?

  1. The Kigali Amendment to the Montreal Protocol
  2. The Codex General Principles of Food Hygiene
  3. The Basel Convention on hazardous waste movements
  4. The Cartagena Protocol on Biosafety
Answer and working

A. The Kigali Amendment to the Montreal Protocol

The 2016 Kigali Amendment added HFCs to the Montreal Protocol for phase-down because of their global-warming potential. Codex covers food hygiene, Basel hazardous waste movements and Cartagena living modified organisms.

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