GATE — Agricultural Engineering (AG), for dairy engineering aspirants · India · IITs and IISc on rotation
Original practice questions written to the published syllabus · not past papersGATE — Agricultural Engineering (AG), for dairy engineering aspirants is a postgraduate admission exam run by IITs and IISc on rotation, for candidates in India.
Official site: gate2026.iitg.ac.in.
We have not been able to confirm these details against the exam body's own specification, so fees, dates and pass marks are left out on purpose. Check the current format, eligibility, fees and dates on the official site.
Engineering calculations that underpin plant design: mass and energy balances, heat duty and regeneration, pump power, flow velocity and holding time. Numerical answer types reward careful units.
Planning a dairy plant from product mix to building: location, layout, equipment sizing, pressure vessels, costing and commissioning.
Our 15 GATE questions in this subject: 0 easy, 10 medium, 5 hard, across 4 units.
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.
A filler is rated at 6,000 packs per hour of 500 mL and runs at 85 percent efficiency. What pasteuriser flow does it actually take?
B. 2,550 litres per hour
Filler throughput = 6,000 × 0.5 L × 0.85 = 2,550 L/h. 3,000 L/h ignores efficiency; 5,100 L/h treats packs as one litre; 3,530 L/h divides by the efficiency instead of multiplying.
Using a Pearson square, how much whole milk of 4.5 percent fat and skim milk of 0.05 percent fat make 1,000 kg of milk standardised to 3.0 percent fat?
B. About 663 kg whole milk and 337 kg skim milk
Parts of whole milk = 3.0 − 0.05 = 2.95; parts of skim = 4.5 − 3.0 = 1.5; whole = 1,000 × 2.95/4.45 = 663 kg, skim = 337 kg. Swapping gives the reverse mix; 667/333 ignores the skim fat; equal parts would give about 2.3% fat.
Milk flows at 20,000 kg per hour and is heated from 4 °C to 72 °C. Taking cp = 3.9 kJ/kg·K, what heat duty is needed without regeneration?
A. About 1,473 kW
Q = m·cp·ΔT = (20,000/3,600) × 3.9 × 68 = 1,473 kW. 5,304 kW converts the flow by dividing by 1,000 instead of 3,600; 1,560 kW uses 72 K instead of 68 K; 1,387 kW uses 64 K.
In a plate pasteuriser, milk enters at 4 °C, leaves the regeneration section at 60 °C and is pasteurised at 72 °C. With equal flows, what is the regeneration efficiency?
A. About 82 percent
Efficiency = (60 − 4)/(72 − 4) = 56/68 = 82%. 78% uses 56/72; 83% uses 60/72; 88% uses 60/68. The denominator is the total rise the heating would need, from inlet to pasteurisation temperature.
A thin cylindrical vessel of 1.5 m diameter and 6 mm wall carries an internal pressure of 0.6 MPa. What are the hoop and longitudinal stresses?
C. 75 MPa hoop and 37.5 MPa longitudinal
Hoop stress = PD/(2t) = 0.6 × 1,500/(2 × 6) = 75 MPa; longitudinal = PD/(4t) = 37.5 MPa. Swapping them reverses the formulas; 150/75 forgets the factor of 2; equal stresses describe a sphere, not a cylinder.
Using the ASME Section VIII Division 1 rule t = PR/(SE − 0.6P), find the required shell thickness for P = 1.0 MPa, inside radius 500 mm, S = 138 MPa and E = 0.85, before corrosion allowance.
D. About 4.3 mm
t = 1.0 × 500/(138 × 0.85 − 0.6 × 1.0) = 500/116.7 = 4.28 mm. 3.6 mm ignores the joint efficiency (500/137.4); 8.6 mm uses the 1,000 mm diameter in place of the radius; 5.0 mm applies the joint efficiency twice. Corrosion allowance is then added and the plate rounded up.
A raw milk silo must hold 80,000 litres of working volume, filled to 90 percent of total capacity. What total capacity is needed?
D. About 88,900 litres
Total = 80,000 ÷ 0.9 = 88,889 L. 72,000 L multiplies by 0.9; 88,000 L adds 10% of 80,000 instead of dividing; 80,000 L has no headspace.
Milk flows at 12,000 litres per hour through a holding tube of 47.5 mm inside diameter. What is the mean velocity?
B. About 1.88 m/s
Q = 12,000/3,600,000 = 0.00333 m³/s; area = π × 0.0475²/4 = 0.00177 m²; v = 0.00333/0.00177 = 1.88 m/s. 0.47 m/s leaves the 1/4 out of the area formula; 7.52 m/s uses the radius in place of the diameter; 3.76 m/s is twice the mean, which is the centreline velocity in laminar flow, not the mean.
A buffer tank must cover a 20-minute filler stoppage while the pasteuriser continues at 15,000 litres per hour. What working volume is needed?
A. 5,000 litres
Volume = 15,000 × 20/60 = 5,000 L. 300,000 L multiplies by 20 without converting minutes to hours; 750 L divides by 20; 12,500 L uses 50 minutes.
A CIP circuit must achieve 1.5 m/s at a flow of 20 cubic metres per hour. What inside pipe diameter gives exactly that velocity?
B. About 69 mm
Area = Q/v = (20/3,600)/1.5 = 0.00370 m²; D = √(4A/π) = 0.0687 m = 69 mm. 49 mm uses √(2A/π) and 97 mm uses √(8A/π), both slips in the area formula; 35 mm is the radius, not the diameter.
This plan follows where our questions actually fall, so the time goes where the marks are likely to be. It is our reading of the syllabus, not the exam body's weighting.
Read the manual chapters for these first and do every worked question you can find on them.
Aim for one sitting per unit, then mixed questions across them.
Come back to these after a first pass, untimed, and read every explanation, including for the options you rejected.
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