JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech III FUNDAMENTALS OF MECHANICAL ENGINEERING Previous Question Paper (February - 2022 - R16)

The Zeroth Law of Thermodynamics states that if two systems are each in thermal equilibrium with a third system, then they are in thermal equilibrium with each other. This law provides the fundamental basis for the measurement of temperature.

If system A is in thermal equilibrium with system C, and system B is in thermal equilibrium with system C, then system A and system B are also in thermal equilibrium. This implies that all three systems share the same temperature property.

The primary application of this law is the construction and calibration of thermometers. By using a thermometer as the 'third system', we can compare the temperatures of two different bodies without bringing them into direct physical contact. It allows for the definition of a consistent temperature scale, such as the Celsius or Kelvin scales, which is essential for all thermodynamic measurements and heat transfer analysis.

Specific heat capacity (c) is defined as the amount of heat energy required to raise the temperature of a unit mass of a substance by one degree. It is a critical property for understanding how materials store thermal energy. A high specific heat capacity means a substance can absorb or release large amounts of heat with minimal temperature change, which is vital in applications like heat exchangers, engine cooling systems, and thermal energy storage. The relationship is given by:

Specific enthalpy (h) is the total heat content per unit mass of a system, defined as the sum of internal energy (u) and the product of pressure (P) and specific volume (v). It represents the energy associated with a substance that can be transferred as heat or work during constant pressure processes. It is essential in the analysis of open systems, such as turbines, compressors, and nozzles, where flow work is significant. The formula is:

Together, these properties allow engineers to calculate energy balances, predict temperature changes, and determine the performance of thermodynamic cycles in power plants and refrigeration systems.