ICAR AIEEA-PG — Agricultural Engineering & Technology (Major Subject Group 10) · India · National Testing Agency for ICAR
Original practice questions written to the published syllabus · not past papersRefrigeration cycles, equipment and cold-store design, from COP to the heat load of a room full of potatoes.
In the exams: GATE AG Section 7 (refrigeration COP/TR in 4 of 8 papers 2019–26; composite cold-store walls recur); ICAR AIEEA-PG Unit VI; ICAR AICE subject 38 Unit 6
ICAR AIEEA-PG — Agricultural Engineering & Technology
Unit VI asks single-answer MCQs on refrigeration and air-conditioning, cold stores and heating and cooling load calculation: the four processes of the cycle, TR definition, refrigerant designation and ODP/GWP, absorption pairs, expansion devices, psychrometric processes, cold-store load components, insulation and vapour-barrier placement. Negative marking rewards precise definitions.
How our questions for ICAR AIEEA-PG spread across the units of Refrigeration, Air-Conditioning & Cold-Chain Engineering. Difficulty: 31 easy, 35 medium, 2 hard.
| Refrigerants: ODP and GWP | 7 | |
| Psychrometric air-conditioning processes | 6 | |
| Cold-store heat load: transmission, product and respiration | 6 | |
| Refrigerated transport and cold-chain logistics | 6 | |
| Vapour-compression refrigeration cycle | 5 | |
| Pressure-enthalpy charts | 5 | |
| Cold-store heat load: infiltration, occupancy and equipment | 5 | |
| Vapour-absorption refrigeration | 4 | |
| COP and tonnes of refrigeration | 4 | |
| Compressors | 4 | |
| Condensers and evaporators | 4 | |
| Expansion devices | 4 | |
| Insulation and vapour barriers | 4 | |
| Ice-bank systems | 4 |
Choose an answer, then open the working. Each explanation says why the right answer is right and why the others are not.
Subcooling the liquid refrigerant leaving the condenser, with evaporating and condensing pressures unchanged, will
B. Increase the refrigerating effect per kg without increasing compressor work per kg
Subcooling lowers h3, and since h4 = h3 the refrigerating effect h1 − h4 grows. Suction state 1 is unchanged, so the work h2 − h1 is unchanged and COP rises. Throttling being isenthalpic is exactly why the lower h3 carries through to h4.
Further reading: Arora, Refrigeration and Air Conditioning
In the three-fluid (diffusion) absorption refrigerator, hydrogen is used to
B. Equalise total pressure throughout the circuit so that no solution pump is needed
Hydrogen fills the evaporator and absorber so that ammonia evaporates at a low partial pressure while total pressure is uniform; circulation is by a heat-driven bubble pump and gravity. Water, not hydrogen, is the absorbent, and ammonia is the refrigerant.
Further reading: Arora, Refrigeration and Air Conditioning
At the evaporator pressure, saturated liquid enthalpy is 180 kJ/kg and saturated vapour enthalpy 390 kJ/kg. Liquid at 250 kJ/kg is throttled into the evaporator. The dryness fraction at evaporator inlet is
B. 0.333
x = (h4 − h_f)/(h_g − h_f) = (250 − 180)/(390 − 180) = 70/210 = 0.333. 0.667 is the liquid fraction; h4/h_g ignores the liquid enthalpy datum. 0.641 is h4/h_g (250/390), and 0.359 is (h_g − h4)/h_g (140/390).
Further reading: Arora, Refrigeration and Air Conditioning
As the evaporating temperature of a reciprocating compressor falls with condensing temperature fixed, its volumetric efficiency
B. Falls, as a higher pressure ratio makes clearance gas re-expand over more stroke
η_v = 1 + C − C(p_d/p_s)^(1/n) falls as p_d/p_s rises. Suction gas actually becomes less dense at lower evaporating temperature, which also reduces mass flow.
Further reading: Arora, Refrigeration and Air Conditioning
A thermostatic expansion valve is designed to maintain a nearly constant
B. Superheat of vapour at the evaporator outlet
The bulb on the suction line senses outlet temperature, and the diaphragm balances bulb pressure against evaporator pressure plus spring: the controlled variable is superheat. Constant evaporator pressure is the automatic (constant-pressure) valve; liquid level is a float valve.
Further reading: Arora, Refrigeration and Air Conditioning
A practical advantage of the capillary tube is that it allows a low-starting-torque compressor motor because
A. High- and low-side pressures equalise through it while the compressor is off
With no valve to close, pressures balance during the off cycle, so the compressor starts against no pressure difference. It has no reserve, no adjustment, and flash gas still forms.
Further reading: Arora, Refrigeration and Air Conditioning
During sensible heating of moist air, which property remains constant?
D. Humidity ratio
No moisture is added or removed, so ω stays constant and the process is horizontal on the chart. Relative humidity falls because the saturation pressure rises; wet-bulb and enthalpy rise.
Further reading: ASABE D271
By Siebel's relation, the specific heat above freezing of a fruit with 80% water is about
D. 3.52 kJ/kg K
c_p = 3.35 × 0.8 + 0.84 = 3.52 kJ/kg K. 1.85 is the below-freezing relation; omitting the 0.84 solids term gives 2.68.
Further reading: Singh and Heldman, Introduction to Food Engineering
In a cold-store wall, the vapour barrier should be placed
D. On the warm (outer) side of the insulation
Vapour moves from warm to cold. A barrier on the warm side stops it before it reaches layers cold enough to condense or freeze it. A tight barrier on the cold side traps any moisture that enters.
Further reading: ASHRAE Handbook — Refrigeration
In the cold chain, the step that removes field heat from produce immediately after harvest is called
A. Pre-cooling
Pre-cooling (forced-air, hydro, vacuum, room or ice cooling) brings produce quickly toward storage temperature. Curing heals wounds at warm temperatures; blanching is a heat treatment before freezing vegetables.
Further reading: ASHRAE Handbook — Refrigeration
Ten here, 68 in the app. The Laisha app has every practice question we have written to ICAR AIEEA-PG in this subject, marked as you go, with timed papers, a jump-to-unanswered list and a certificate when you pass at 70 per cent.
Free for ten days, then one subscription of US$10 a month. We would rather say so here than have you find it later.
An AI operating system for agriculture: free guides, manuals and tools written for every country.