During sensible heating of moist air, enthalpya)Increasesb)Decreasesc)Remains samed)Can increase or decreaseCorrect answer is option 'A'. Can you explain this answer?

Question

Answer

Sensible heating

During this process, the moisture content of air remains constant, and its temperature increases as it flows over a heating coil. The heat transfer rate during this process is given by:

Q_h = m_a(h_B−h_o) = m_ac_pm(T_B−T_o)

where c_pm is the humid specific heat (≈1.0216 kJ/kg dry air), tangent direction, and ma is the mass flow rate of dry air (kg/s).

Sensible heating process

on psychrometric chart

During sensible heating of moist air, enthalpy increases.
Sensible cooling:
During this process, the moisture content of air remains constant, but its temperature decreases as it flows over a cooling coil.

Sensible cooling process

on psychrometric chart

Answer

Sensible heating

During this process, the moisture content of air remains constant, and its temperature increases as it flows over a heating coil. The heat transfer rate during this process is given by:

Q_h = m_a(h_B−h_o) = m_ac_pm(T_B−T_o)

where c_pm is the humid specific heat (≈1.0216 kJ/kg dry air), tangent direction, and ma is the mass flow rate of dry air (kg/s).

Sensible heating process

on psychrometric chart

During sensible heating of moist air, enthalpy increases.
Sensible cooling:
During this process, the moisture content of air remains constant, but its temperature decreases as it flows over a cooling coil.

Sensible cooling process

on psychrometric chart

Answer

Enthalpy and Sensible Heating of Moist Air

Introduction:
Enthalpy is a thermodynamic property that describes the total energy of a system, including its internal energy and the work done on or by the system. Sensible heating refers to the process of increasing the temperature of a substance without changing its phase.

Explanation:
During sensible heating of moist air, the enthalpy increases. This is due to the addition of heat energy to the air, which increases its internal energy and, consequently, its enthalpy.

Reasoning:
When heat is added to moist air, the energy is transferred to the air molecules. The increased energy causes the molecules to move faster and collide more frequently, resulting in an increase in temperature. This increase in temperature corresponds to an increase in the internal energy of the air.

Key Points:
- Sensible heating involves the addition of heat energy to a substance without changing its phase.
- Enthalpy is a thermodynamic property that describes the total energy of a system.
- During sensible heating of moist air, the enthalpy increases due to the addition of heat energy.
- The increase in temperature of the moist air corresponds to an increase in its internal energy.
- Sensible heating is commonly used in various applications, such as heating systems, industrial processes, and climate control.

Conclusion:
During sensible heating of moist air, the enthalpy increases as heat energy is added to the air. This results in an increase in temperature and internal energy of the air molecules. Sensible heating is an important process used in various applications to control and regulate the temperature of air.

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