Energetics
LATENT HEAT, or hidden heat, is the term used for the heat absorbed or given off by a substance while it is changing its physical state. When this occurs, the heat given off or absorbed does NOT cause a temperature change in the substance. In other words, sensible heat is the term for heat that affects the temperature of things; latent heat is the term for heat that affects the physical state of things. To understand the concept of latent heat, you must realize that many substances may exist as solids, as liquids, or as gases, depending primarily upon the temperatures and pressure to which they are subjected. To change a solid to a liquid or a liquid to a gas, ADD HEAT; to change a gas to a liquid or a liquid to a solid, REMOVE HEAT. Suppose you take an uncovered pan of cold water and put it over a burner. The sensible heat of the water increases and so does the temperature. As you continue adding heat to the water in the pan, the temperature of the water continues to rise until it reaches 212°F. What is happening?
SPECIFIC HEAT
SPECIFIC HEAT is the ratio between the quantity of heat required to change the temperature of 1 pound of any substance 1°F, as compared to the quantity of heat required to change 1 pound of water 1°F. Specific heat is equal to the number of Btu required to raise the temperature of 1 pound of a substance 1o F. For example, the specific heat of milk is .92, which means that 92 Btu will be needed to raise 100 pounds of milk 1o F. The specific heat of water is 1, by adoption as a standard, and specific heat of another substance (solid, liquid, or gas) is determined experimentally by comparing it to water. Specific heat also expresses the heat-holding capacity of a substance compared to that of water.
TRANSFER OF HEAT
Heat flows from a substance of higher temperature to bodies of lower temperature in the same manner that water flows down a hill, and like water, it can be raised again to a higher level so that it may repeat its cycle. When two substances of different temperatures are brought in contact with each other, the heat will immediately flow from the warmer substance to the colder substance.
MEASUREMENT OF HEAT
The usual means of measuring temperature is a thermometer. It measures the degree or intensity of heat and usually consists of a glass tube with a bulb at the lower portion of the tube that contains mercury, colored alcohol, or a volatile liquid. The nature of these liquids causes them to rise or fall uniformly in the hollow tube with each degree in temperature change. Thermometers are used to calibrate the controls of refrigeration. The two most common thermometer scales are the Fahrenheit and the Celsius. On the Fahrenheit scale, there is a difference of 180° between freezing (32°) and the boiling point (212°) of water. On the Celsius scale, you have only 100° difference between the same points (0° freezing and 100° boiling point).
The refrigeration system consists of four basic components-.............................., and the control devices.
In this compressor, the electric motor and compressor are both in the same airtight housing and share the same shaft.
Every engineer __________ accurately the amount of any change in material in different conditions.
A discharge pressure gauge and thermometer are installed in the compressor discharge line (liquid line) to show ...
We convert energy from one form to another…
Convective heat transfer, or convection, is the transfer … heat … one place… another … the movement … fluids, a process that is essentially the transfer … heat… mass transfer. Bulk motion … fluid enhances heat transfer … many physical situations, such as (for example) between a solid surface and the fluid. Convection is usually the dominant form … heat transfer … liquids and gases.
Choose the right variant:
All refrigeration and air conditioning processes used / use a gas to facilitate the transfer of heat between the air-conditioned area and the outside atmosphere. This process rely / relies on the use of a compressor to increase / increases the pressure in the evaporator section, or air conditioned area, of the system which in turn allowing / allows the absorption of heat from that area. This absorb / absorbed heat and any heat generate / generated by the compression process needs / need to be rapidly removed from the refrigerant in the outside, or condenser, part of the system so that the cycle of heat transfer can be repeated / repeat. This is typically doing / done by allowing/ allow the hot refrigerant to circulate / circulates through a series of tubes exposed to a fan induced airflow.
Thermistors are used
We _________about the energy «consumption» or energy «transformation in reference to the average energy released by the combustion of fossil fuels.
Назва «потенційна енергія» буде означати думку, що енергія могла би легко передаватися як робота.
Дозвольте зауважити, що коли швидкість об’єкта подвоюється, його кінетична енергія збільшується в чотири рази.
An energy storage device made up of one or more complex conductor cells may be called a battery
Read the sentence and define the tense:
Scientists have attempted to separate all forms of energy.
Read the sentence and define the tense:
The impact of man on nature has obtained a dramatic character today. With the development of civilization man's interference in nature has increased.
Read the sentence and define the tense:
They proved that the apparent mass of an electron was nearly constant for velocities less than one-tenth that of light.
Modern refrigeration has many applications, such as preserving medicine, blood, and the most important application, the preservation of food. Most foods kept at room temperature spoil rapidly. This is due to the rapid growth of bacteria. Refrigeration preserves food by keeping it cold, which greatly slows down the growth of bacteria. In days past, blocks of ice were used in iceboxes to refrigerate food and other items. These iceboxes were small and not very practical. Today, mechanical refrigeration systems make transportation, storage, and use of refrigerated goods easy and practical. The installation, operation, adjustment, and repair of refrigeration equipment are the primary responsibility of the Utilitiesman rating. To perform these duties required of a refrigeration mechanic, you need to understand...
(choose five)
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