Explanation:
<u>(a)</u>
<u>The measure of material's ability to conduct thermal energy (heat) is known as thermal conductivity.</u> For examples, metals have high thermal conductivity, it means that they are very efficient at conducting heat.<u> The SI unit of heat capacity is W/m.K.</u>
The expression for thermal conductivity is:
Where,
q is the heat flux
is the thermal conductivity
is the temperature gradient.
<u>(b)</u>
<u>Heat capacity for a substance is defined as the ratio of the amount of energy required to change the temperature of the substance and the magnitude of temperature change. The SI unit of heat capacity is J/K.</u>
The expression for Heat capacity is:
Where,
C is the Heat capacity
E is the energy absorbed/released
is the change in temperature
<u>(c)</u>
<u>Thermal diffusivity is defined as the thermal conductivity divided by specific heat capacity at constant pressure and its density. The Si unit of thermal diffusivity is m²/s.</u>
The expression for thermal diffusivity is:
Where,
is thermal diffusivity
is the thermal conductivity
is specific heat capacity at constant pressure
is density
The first one is the answer
Explanation:
Conduction:
Heat transfer in the conduction occurs due to movement of molecule or we can say that due to movement of electrons in the two end of same the body. Generally, phenomenon of conduction happens in the case of solid . In conduction heat transfer takes places due to direct contact of two bodies.
Convection:
In convection heat transfer of fluid takes place due to density difference .In simple words we can say that heat transfer occur due to motion of fluid.
Answer: The answer is D
D.In hydraulic systems, the operating temperatures must be kept between 170�F and 180°F
Explanation:
The operating temperature for hydraulic systems is 140°F and below. Anything above this temperature is too high and will reduce the useful life of hydraulic fluid.
Most often problems associated with hydraulic systems are caused by fluid contaminated with particulate matter.
Answer:
If everything is working properly, your AC should never need a refrigerant. In fact, a central air conditioner should never need refrigerant added unless there's a refrigerant leak. We'll explain how an AC uses refrigerant and what to do if you think your system is low on refrigerant. OR When you check your air conditioner unit, or your outdoor central air unit with the fan, and see an ice building up on the refrigerant line, then you may be low on freon. ... This will cause the surrounding moisture on the refrigerant line to freeze up. This is a sign you need freon.
Explanation:
(this is according to plumbing services website)
