Question:
The refrigerant and absorbent used in Vapour absorption refrigeration system respectively are
The refrigerant and absorbent used in Vapour absorption refrigeration system respectively are
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Pay close attention to the word "respectively"! In the pairs:
1. Ammonia (Refrigerant) + Water (Absorbent) $\rightarrow$ Used for low-temperature freezing application.
2. Water (Refrigerant) + Lithium Bromide (Absorbent) $\rightarrow$ Limited to air conditioning because water freezes at $0^\circ\text{C}$.
Updated On: Jul 9, 2026
- Water and water
- Lithium bromide and water
- Ammonia and lithium bromide
- Ammonia and water
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The Correct Option is D
Solution and Explanation
Concept:
A Vapour Absorption Refrigeration System (VARS) replaces the power-consuming mechanical compressor of a standard Vapour Compression Refrigeration System (VCRS) with an absorber, a pump, and a generator. It utilizes thermal energy (low-grade heat) rather than mechanical work to drive the refrigeration cycle.
This process requires a working pair consisting of two fluids that have high mutual solubility:
• Refrigerant: The fluid that evaporates at low temperatures to absorb heat from the refrigerated space, producing the cooling effect.
• Absorbent: The fluid that absorbs the refrigerant vapor in the low-pressure absorber and carries it to the high-pressure generator.
Step 1: Evaluate common VARS working pairs.
The two most common commercial fluid combinations used in absorption systems are:
• Aqua-Ammonia System:
• Refrigerant = Ammonia (\(NH_3\))
• Absorbent = Water (\(H_2O\))
• Lithium Bromide-Water System:
• Refrigerant = Water (\(H_2O\))
• Absorbent = Lithium Bromide solution (\(LiBr\))
Step 2: Analyze the options based on standard pairs.
Let us check the ordering required by the question prompt ("refrigerant and absorbent respectively"):
• Option (B) lists "Lithium bromide and water". In a LiBr system, water acts as the refrigerant and Lithium Bromide acts as the absorbent. Since the option reverses this order, it is incorrect.
• Option (D) lists "Ammonia and water". Here, Ammonia is correctly identified as the refrigerant and water as the absorbent, matching the requested sequence. Therefore, the correct pair matching the "refrigerant and absorbent" order is Ammonia and water, corresponding to Option (D).
• Refrigerant: The fluid that evaporates at low temperatures to absorb heat from the refrigerated space, producing the cooling effect.
• Absorbent: The fluid that absorbs the refrigerant vapor in the low-pressure absorber and carries it to the high-pressure generator.
Step 1: Evaluate common VARS working pairs.
The two most common commercial fluid combinations used in absorption systems are:
• Aqua-Ammonia System:
• Refrigerant = Ammonia (\(NH_3\))
• Absorbent = Water (\(H_2O\))
• Lithium Bromide-Water System:
• Refrigerant = Water (\(H_2O\))
• Absorbent = Lithium Bromide solution (\(LiBr\))
Step 2: Analyze the options based on standard pairs.
Let us check the ordering required by the question prompt ("refrigerant and absorbent respectively"):
• Option (B) lists "Lithium bromide and water". In a LiBr system, water acts as the refrigerant and Lithium Bromide acts as the absorbent. Since the option reverses this order, it is incorrect.
• Option (D) lists "Ammonia and water". Here, Ammonia is correctly identified as the refrigerant and water as the absorbent, matching the requested sequence. Therefore, the correct pair matching the "refrigerant and absorbent" order is Ammonia and water, corresponding to Option (D).
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