Which of the following is primarily responsible for energy transfer according to Fourier’s Law?
A Heat flux
B Temperature gradient
C Fluid velocity
D Thermal resistance
Fourier’s Law states that heat transfer through a material is directly proportional to the temperature gradient. A larger temperature difference between two points leads to a greater rate of heat transfer by conduction.
In Newton’s Law of Cooling, what primarily influences the rate of heat loss?
A Heat capacity
B Material conductivity
C Fluid viscosity
D Temperature difference
Newton’s Law of Cooling indicates that the rate of heat loss from an object is proportional to the temperature difference between the object and its surroundings. The larger the difference, the faster the heat transfer.
What does energy balance in thermal systems primarily account for?
A Material resistance
B Energy flow and storage
C Heat capacity
D Surface area
Energy balance in thermal systems involves accounting for the energy entering, leaving, and being stored within a system. It ensures that all energy inputs, outputs, and transformations are accounted for during heat transfer processes.
What is the primary purpose of using Fourier’s Law in heat conduction?
A To predict temperature change
B To calculate heat loss
C To describe heat transfer rate
D To determine thermal resistance
Fourier’s Law is used to describe the rate at which heat is transferred through a material by conduction. It relates the heat transfer rate to the temperature gradient, material conductivity, and cross sectional area.
How does an increase in surface area affect the rate of heat transfer?
A Reduces heat loss
B Increases heat transfer
C Decreases heat transfer
D No effect
Increasing surface area provides more space for heat to be exchanged between materials or fluids, thereby improving the rate of heat transfer. This principle is commonly used in heat exchangers and cooling systems.
What happens when the temperature difference in a system decreases?
A Thermal resistance increases
B Heat transfer increases
C Heat transfer decreases
D Heat transfer stays constant
The rate of heat transfer is directly proportional to the temperature difference. A smaller difference between two regions results in less heat being transferred. This principle is fundamental in both conduction and convection heat transfer.
Which factor primarily influences the rate of heat transfer in convection?
A Thermal conductivity
B Fluid flow velocity
C Surface roughness
D Temperature gradient
In convection, the rate of heat transfer is influenced by the fluid flow velocity. A higher velocity enables the fluid to carry heat more effectively from the heated surface to cooler regions, increasing the overall heat transfer rate.
What type of heat transfer occurs in a solid material?
A Conduction
B Evaporation
C Radiation
D Convection
Conduction is the process of heat transfer in solids, where heat flows from a high temperature region to a lower temperature region by the vibration and collision of particles. This occurs in all solid materials.
Which of the following factors affects the heat transfer rate in a heat exchanger?
A Fluid density
B Surface roughness
C Temperature difference
D Fluid pressure
In a heat exchanger, the rate of heat transfer depends primarily on the temperature difference between the fluids involved. The greater the temperature difference, the higher the rate of heat exchange.
What is the role of thermal resistance in heat transfer?
A Increases heat transfer
B No effect
C Accelerates heat flow
D Reduces heat transfer
Thermal resistance opposes the flow of heat. A higher thermal resistance means less heat is transferred through the material. It is inversely related to thermal conductivity and is crucial in insulating materials.
In heat transfer, what is the effect of increasing the temperature of the heat source?
A Reduces thermal resistance
B Increases heat transfer
C No effect
D Reduces heat transfer
Increasing the temperature of the heat source enhances the temperature gradient between the source and the surrounding medium. This results in a higher rate of heat transfer according to Fourier’s and Newton’s laws.
How does Newton’s Law of Cooling relate to heat transfer?
A It measures energy storage
B It calculates heat capacity
C It predicts heat flow due to temperature difference
D It defines thermal conductivity
Newton’s Law of Cooling predicts the rate of heat flow from an object based on the temperature difference between the object and its environment. The greater the difference, the faster the heat is transferred from the object.
What happens to heat transfer when the thermal conductivity of a material increases?
A Heat transfer decreases
B Thermal resistance increases
C Heat transfer stays constant
D Heat transfer increases
Thermal conductivity determines how well a material conducts heat. As thermal conductivity increases, the material becomes a better conductor, allowing more heat to flow through it, thereby increasing the rate of heat transfer.
What is the relationship between the temperature gradient and heat flux in conduction?
A Constant
B Directly proportional
C Inversely proportional
D No relationship
In conduction, the heat flux (rate of heat transfer per unit area) is directly proportional to the temperature gradient. A higher temperature gradient results in a higher heat flux, leading to increased heat transfer.
How does energy balance relate to heat transfer in thermal systems?
A It ensures conservation of energy
B It calculates energy storage
C It measures heat loss
D It determines heat flow
Energy balance in thermal systems ensures that all energy entering, leaving, and being stored in a system is accounted for. It helps in analyzing heat transfer by ensuring the law of conservation of energy is applied.