Does heat transfer require temperature difference? The transfer of heat can occur in three ways: conduction, convection, and radiation.
Heat transfer occurs between states of matter whenever a temperature difference exists
and heat transfer occurs only in the direction of decreasing temperature, meaning from a hot object to a cold object.
Can heat transfer occur without temperature difference?
Conduction and convection rely on temperature differences
; radiation does, too, but with radiation the absolute temperature is important. In some cases one method of heat transfer may dominate over the other two, but often heat transfer occurs via two, or even all three, processes simultaneously.
Is a temperature difference necessary for heat flow?
“Thermal Energy (HEAT) can only flow from objects of higher temperature to objects of lower temperature.” THERMAL EQUILIBRIUM – Notice that
the only requirement shared by all forms of energy transfer is a temperature difference between the objects
.
Does temperature difference affect transfer rate?
What does heat transfer depend on?
Experiments show that the heat transferred to or from a substance depends on three factors—
the change in the substance’s temperature, the mass of the substance, and certain physical properties related to the phase of the substance
.
Is a temperature difference necessary to operate a heat engine?
Yes, the temperature difference is necessary for the heat engine to operate in a cycle.
What conditions are necessary for heat transfer?
Key Concepts. The transfer of heat can occur in three ways: conduction, convection, and radiation. Heat transfer occurs between states of matter
whenever a temperature difference exists
and heat transfer occurs only in the direction of decreasing temperature, meaning from a hot object to a cold object.
Which of the following in not a method of heat transfer?
Ultraviolet radiation
is not a method of heat transfer. While cooking, heat transfer occurs only through conduction, convection, or radiation.
Why is there a difference in temperature?
The temperature difference is generally caused by
heat remaining trapped within locations that often resemble concrete jungles
. The temperature variation can range between three to five degrees Celsius. Why are cities hotter than rural areas?
Will the heat be transferred if the temperature of two objects is the same?
Temperature is a measure of the average kinetic energy of the atoms or molecules in the system. The zeroth law of thermodynamics says that
no heat is transferred between two objects in thermal equilibrium
; therefore, they are the same temperature.
Does heat transfer coefficient change with temperature?
In forced convection heat transfer, the heat transfer coefficient of air
may not affected by changing the temperature
as the change in its properties (Prandtl number, viscosity, ….) is very small compared with momentum force variation.
1: The heat Q transferred to cause a temperature change depends on the magnitude of the temperature change, the mass of the system, and the substance and phase involved. (a) The amount of heat transferred is
directly proportional
to the temperature change.
Is heat loss proportional to temperature difference?
Newton’s law of cooling states that the rate of heat loss of a body is
directly proportional
to the difference in the temperatures between the body and its environment.
What factors affect heat transfer coefficient?
Heat transfer coefficient depends on both
the thermal properties of a medium, the hydrodynamic characteristics of its flow, and the hydrodynamic and thermal boundary conditions
.
What are the factors affecting the amount of heat conducted?
The process of heat conduction depends on four basic factors:
the temperature gradient, the cross section of the materials involved, their path length, and the properties of those materials
.
Can a heat engine operate with only a high temperature heat reservoir?
The answer is
NO, because without the cooling in condenser the cycle cannot be completed
. Every heat engine must waste some energy by transferring it to a low-temperature reservoir in order to complete the cycle, even in idealized cycle.
Why is a heat engine not 100% efficient?
A heat engine is considered to be 100% efficient if only all the heat is converted into useful work or mechanical energy. Since
heat engines cannot convert all the heat energy into mechanical energy
, their efficiency can never be 100%.
Why does a heat engine need a cold reservoir?
Which of the following is not true about the mode of heat transfer?
How does convection transfer heat?
Convection. Convective heat transfer is the transfer of heat between two bodies
by currents of moving gas or fluid
. In free convection, air or water moves away from the heated body as the warm air or water rises and is replaced by a cooler parcel of air or water.
Which of the following is required in order for all methods of heat transfer to happen?
Heat can travel from one place to another in three ways: Conduction, Convection and Radiation. Both
conduction and convection require matter to transfer heat
. If there is a temperature difference between two systems heat will always find a way to transfer from the higher to lower system.
What are the different ways of heat transfer?
- Conduction is the transfer of energy from one molecule to another by direct contact. …
- Convection is the movement of heat by a fluid such as water or air. …
- Radiation is the transfer of heat by electromagnetic waves.
What happens if two objects with different temperatures come in contact with each other?
Can there be any heat transfer between two bodies that are at the same temperature but at different pressures?
yes it’s possible if the states are somehow not reversible
(might not be the proper word for that). For example if you have water and air at ambient temperature then water will evaporate as long as the air isnt saturated.
Can two bodies with different temperatures have thermal equilibrium?
Two bodies are said to be in thermal equilibrium, when no heat is exchanged between then,
this is possible only if they both are of the same temperature
, because a difference in temperature will lead to exchange in heat to equalize the temperature.
Which of the following statements is incorrect by heat transfer?
Which of the following statement is incorrect according to heat transfer? Explanation:
Heat flows from higher to lower temperature
. Explanation: t
w
= t
a
+ q
g
R/ 2h. Explanation: t = t
w
+ q
g
(R
2
– r
2
)/4k.
How does the temperature difference between two containers relate to the rate of temperature change?
Is convective heat transfer coefficient temperature dependent?
The constant of proportionality is the heat transfer coefficient. The law applies when the coefficient is independent, or relatively independent, of the temperature difference between object and environment.
In classical natural convective heat transfer, the heat transfer coefficient is dependent on the temperature
.
What slows the transfer of heat?
What is difference between heat transfer coefficient and thermal conductivity?
Does heat transfer coefficient depend on material?
Heat transfer coefficient is not a thermophysical property of material, while
it depends on the surface geometry and the conditions of boundary layer
.
What does convection coefficient depend on?
How could there be a change in heat without a change in temperature?
In general,
whenever there is a change of state, such as the solid-liquid or the liquid-gas transition
, heat energy can be added without a temperature change. The change of state requires energy, so added energy goes into that instead of increasing the temperature.
Can an object be hotter than another if they are at same temperature?
Can one object be hotter than another if they are at the same temperature? Explain. A:
No, what we mean by ‘hotter’ (in this context) is ‘having higher temperature’, so by definition that’s impossible.
Which of the following is not a method of heat transfer?
Ultraviolet radiation
is not a method of heat transfer. While cooking, heat transfer occurs only through conduction, convection, or radiation.
