Thermal Engineering Fundamentals

What is the first law of thermodynamics?

• The total energy in a closed system is always increasing.

• Heat is always converted to work: Q = W.

• Energy conservation principle: ΔU = Q - W.

• Energy cannot be created or destroyed: E = mc².

Explain the concept of enthalpy in thermodynamics.

• Enthalpy is the measure of a system's temperature only.

• Enthalpy is the energy required to change the state of a substance.

• Enthalpy is the total heat content of a system, defined as H = U + PV, where H is enthalpy, U is internal energy, P is pressure, and V is volume.

• Enthalpy is the difference between kinetic and potential energy in a system.

What is Bernoulli's principle in fluid mechanics?

• Bernoulli's principle describes the relationship between the speed of a fluid and its pressure, indicating that higher fluid speed results in lower pressure.

• Bernoulli's principle states that pressure increases with fluid speed.

• Bernoulli's principle applies only to gases, not liquids.

• Bernoulli's principle indicates that fluid speed and pressure are unrelated.

Define viscosity and its significance in fluid flow.

• Viscosity is a measure of a fluid's resistance to flow, significant for determining flow behavior and energy loss in fluid systems.

• Viscosity is the speed at which a fluid flows through a pipe.

• Viscosity measures the color of a fluid in motion.

• Viscosity is the temperature of a fluid affecting its density.

What are the three main methods of energy conversion?

• Radiant conversion

• Mechanical conversion, Thermal conversion, Chemical conversion

• Nuclear conversion

• Electrical conversion

Describe the process of conduction in heat transfer.

• Conduction is the transfer of heat through direct contact of particles in a material.

• Conduction requires a vacuum to occur.

• Conduction is the transfer of heat through radiation.

• Conduction occurs only in gases and liquids.

What is the difference between specific heat and latent heat?

• Specific heat is the heat required to melt a substance.

• Specific heat relates to temperature change, while latent heat relates to phase change.

• Specific heat and latent heat are the same concept.

• Latent heat is the heat required to raise the temperature of a substance.

How does pressure affect the boiling point of a liquid?

• Increasing pressure lowers the boiling point; decreasing pressure raises it.

• Pressure has no effect on the boiling point of a liquid.

• Higher temperatures always lead to a higher boiling point regardless of pressure.

• Increasing pressure raises the boiling point; decreasing pressure lowers it.

What are the properties of materials that affect thermal conductivity?

• Atomic structure, density, temperature, phase, and bonding type.

• Color and texture

• Magnetic properties

• Electrical conductivity

Explain the concept of thermal equilibrium.

• Thermal equilibrium is the process of heating a body until it reaches a boiling point.

• Thermal equilibrium is the state in which two or more bodies in thermal contact have the same temperature, resulting in no net heat flow between them.

• Thermal equilibrium occurs when bodies are at different temperatures and heat flows between them.

• Thermal equilibrium refers to the condition where bodies are in motion and exchange kinetic energy.