Which of the following is used as a cooling agent in refrigerator?

JIPMER Nursing Officer-2024

Non Nursing Subjects

Easy

Appeared in: JIPMER Nursing Officer-2024

Explanation

Liquid ammonia is a common refrigerant, especially in large-scale industrial and absorption refrigerators, where it is known as R-717.
It possesses a high latent heat of vaporization, meaning it absorbs a significant amount of heat when it evaporates, making it very effective for cooling.
Compared to the other options, ammonia's boiling point is suitable for standard refrigeration cycles, whereas the others are cryogenic liquids used for much lower temperatures.

Option A: Liquid hydrogen has an extremely low boiling point (-252.87 °C) and is highly flammable. It is used as a rocket fuel and for cryogenic research, not in conventional refrigeration systems.
Option C: Liquid nitrogen is a cryogenic fluid used for rapid freezing (e.g., preserving biological samples, cryotherapy). It is not used as a circulating refrigerant in a closed-loop system like a standard refrigerator.
Option D: Liquid helium provides the lowest temperatures of any common substance, boiling at -268.93 °C. Its use is limited to highly specialized applications like cooling superconducting magnets in MRI machines and scientific research.

Visual 1: Diagram - A schematic of the vapor-compression refrigeration cycle. This would show the four main components (compressor, condenser, expansion valve, evaporator) and illustrate how the refrigerant (like ammonia) changes state to move heat.
Visual 2: Chart - A comparative chart showing the boiling points and primary applications of various substances, including ammonia, nitrogen, helium, and common freons, to visually distinguish between refrigerants and cryogenic liquids.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Principles of Refrigeration and Chemical Refrigerants as background academic context rather than a clinical decision trigger.
Understanding refrigeration principles is crucial for nurses due to the 'cold chain'—the system for storing and transporting vaccines, blood products, and certain medications at specific temperatures to maintain their potency.
Refrigerators in healthcare settings must maintain a stable temperature, typically between +2°C and +8°C. The technology, whether using ammonia in large systems or other refrigerants, is vital for patient safety and treatment efficacy.
Specialized medical and research applications may use cryogenic freezing with liquid nitrogen or helium to preserve tissues, stem cells, or other biological samples for long periods.

How to Approach the Question

First, identify the key concept in the question: finding a 'cooling agent' for a 'refrigerator'.
This is a knowledge-based question. Recall or deduce the function of a refrigerant in a standard cooling cycle.
Consider the properties of each option. Think about their common uses. Are they used for everyday cooling or for extreme, specialized purposes?
Differentiate between 'refrigeration' (cooling to just above or below 0°C) and 'cryogenics' (achieving extremely low temperatures, below -150°C).
Eliminate the options that are known cryogenic liquids (Hydrogen, Nitrogen, Helium), as they are not used in standard refrigerators.
This leaves Liquid Ammonia, which is a known industrial refrigerant, as the most plausible answer.

Concept Tested & Keywords

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