DEFINITION OF CONCEPTS DEALING WITH HEAT
Knowledge of the effects and nature of heat is necessary for a clear understanding of H.E.A.T. Machine technology. I have included this information for those who have no understanding of heat to have a reference point to study from and gather more information. For those who know something of heat and its effects this will be a review.
Heat is a form of energy, and since it is not a substance, it can only be dealt with only through its effects on substances. Every substance on earth contains some heat, so that when a body is “cold” it means only that the heat which it contains is less concentrated or less intense than the heat in some other body used for comparison. One instructor told me, there is no such thing as cold, only a relative lack of heat.
Absolute zero: As heat is removed from a substance its temperature decreases and there must be some point where there will be no more heat remaining in the substance to be extracted. This point is known as absolute zero (-459.6oF) and has been determined only theoretically.
Measurement of heat: In order to measure the heat in a substance, we must consider (1) the concentration of the heat and (2) the heat holding nature of the substance. The white hot filament of an electric light bulb may contain fewer heat units than a pail of warm water, but in the filament the heat is more highly concentrated. Temperature expresses the concentration of heat in a body, and this concentration is determined by measuring its effect on some other material which has been agreed upon as a standard of measurement. Mercury thermometers are an example of a device in general acceptance.
Heat flow: Heat flows from bodies of higher temperature to bodies of lower temperature in a manner similar to that in which water flows from a higher level to a lower level; and like water, it can be pumped uphill, from which point it can flow away in a different direction. When two substances are brought into thermal contact (so heat can flow) the heat starts to flow from one into the other till their temperatures are equal, at which time the flow stops. The greater the temperature difference between the two bodies, the faster the heat flow; and as the temperature difference approaches zero, the rate of heat flow approaches zero. Heat can flow from one substance to another in three ways, or a combination of these.
(1) Radiation: In radiation, as from the sun, in which no material substance acts as a carrier, radiant heat may pass through a transparent substance without warming it and is stopped or absorbed only by an opaque substance. Usually darker objects will absorb more heat than lighter ones. Like light, radiant heat travels in a straight line from its source and can best be reflected with a polished surface. For this reason, areas that you don’t want to absorb radiant heat should be surfaced with light colored reflective surfaces.
(2) Conduction: In conduction, as through a bar or tube from one end to the other, the heat is passes from one particle of material to the next one touching it. The flow of heat by conduction also takes place on the surface of the object to a liquid or gas touching it.
(3) Convection: Convection is the transfer of heat from a warm body to a cold one by a fluid (liquid or gas) acting as a carrier between the two. In natural convection the fluid usually absorbs heat by conduction, when fluids absorb heat they become lighter and rise (up against gravity). The extra heat is usually given to some other “cooler” medium and the carrier fluid becomes heavy again, dropping down to be heated again. In mechanical convection, the working medium is pumped form the warm to cold bodies and back again. In any convection system, care must be taken to design for the most direct route.
Unit of heat: The “amount of heat” added to, or subtracted from, a body can be measured best by the rise and fall in the temperature of a known weight of a substance. As a standard for all heat measurement, the unit of heat has been agreed upon to be 1/180 part of the heat required to raise the temperature of 1 pound of water from 32oF to 212oF at atmospheric pressure. This amount of heat is known as the British thermal unit, or BTU.
Specific heat: The specific heat of a substance is the ratio of the heat required to raise the temperature of a unit weight of the substance 1o to the heat required to raise the temperature of water 1o at some specified temperature. The specific heat is thus numerically equal to the number of BTU’s required to raise the temperature of one pound of the substance through 1oF. The specific heat of water is 1 by adoption as standard and the specific heat of another substance (solid, liquid or gas) is determined experimentally by comparing it with water. Specific heat expresses the heat holding nature of a substance compared to the heat holding capability of water.
Sensible heat: Heat added to (or subtracted from) a substance without causing a change in state will cause an increase (or decrease) in temperature that can be measured with a thermometer.
Latent heat: This is heat added (or subtracted) from a substance that can’t be measured with a thermometer. This is the heat required for a substance to “change its state” at its freezing or boiling point. If it is at its freezing point, it is called the latent heat of fusion. If it is at its boiling point, and is going from a liquid to a gas, it is called its latent heat of vaporization. If it is at its boiling point, and is going from a gas to a liquid, it is sometimes called its latent heat of condensation.
A solid won’t get hotter than its freezing point no matter how much heat is applied, it will simply thaw faster. The resulting liquid can then continue to rise in temperature with “sensible heat”.
Increasing the pressure on a substance will raise its freezing or boiling temperature but will not affect its latent heat of fusion or evaporation.
Decreasing the pressure on a substance will lower its freezing or boiling temperature but will not affect its latent heat of fusion or evaporation.
The latent heat of fusion of water at 32oF at atmospheric pressure is 144 BTU per pound (freezing or melting)
The latent heat of vaporization of water at 212oF at atmospheric pressure is 970.3 BTU per pound (condensing or evaporating).
Total heat: Since measurements of the total heat in a certain weight of a substance cannot be started at absolute zero, a temperature is adopted at which it is assumed there is no heat and tables of data are constructed on that basis for practical use. Data tables giving the heat content of most commonly used refrigerants start at -40oF below zero as the assumed point of no heat; tables for water and steam start at 32oF above zero. Data tables usually show a notation showing the starting point for heat content measurement.
Insulation: There would be no way for refrigeration systems to work if insulation was not applied to enclose the area being cooled. Insulation should be applied that effectively reduces heat transfer to your cooled area by radiation, conduction and convection.
Refrigerants: A liquid has different boiling temperatures (points) for different pressures under which is confined. The boiling point is also the condensation point for that pressure. This pressure-temperature relation must be determined experimentally for each liquid.
Water boils at 212oF at atmospheric pressure (14.7 psi absolute or zero psi gauge). Water boils at 100oF at 28 inches of vacuum, Hg (.98 psi absolute) and at 338oF at 100 psi (gauge)
Because most liquids used as refrigerants have low boiling points, they can not exist as liquids at ordinary atmospheric temperatures and pressures. They are held as liquids by confining them under higher pressures.
Usually if refrigerant liquids are simply confined in a container, at atmospheric temperature, some of the liquid will turn to vapor, thus pressurizing the container enough that the rest of the liquid will stay in the liquid state. If outside temperatures go up, a little more of the liquid will vaporize and the container’s interior pressure will rise again to maintain the rest of the liquid as liquid. If outside temperatures go down, container pressures drop as it losses heat.
So cooling the container is a good way to reduce pressure and/or cause the gasses to lose their latent heat of vaporization and condense.
Critical temperature: The temperature beyond which a liquid can no longer exist as a liquid, no matter how much pressure is applied.
Critical pressure: The maximum pressure that can be applied to a liquid to prevent it from changing into a gas.
Beyond the critical temperature and pressure point of a liquid, it will turn into a gas. If you don’t have a container strong enough to hold the pressure resulting in the sudden expansion of liquid to gas in an enclosed area, then your container will explode.
My brother and I learned this the hard way. Interestingly enough, it was on the exact same day the space shuttle Challenger blew up.
Saturated Refrigerant: When the temperature of a liquid is raised to the boiling point corresponding with its pressure, both liquid and gas exist together and the condition is called saturated. Below the boiling point it is only liquid. Above the boiling point it is only gas and becomes what is called superheated gas.
Strictly speaking, saturated gas is “vapor” until it is superheated and then it is a gas.
Evaporator: The evaporator provides contact for the refrigerant gasses and the area (substance) to be cooled. Liquid refrigerant in the evaporator is maintained at a low enough pressure that it is well below its boiling point for the temperature of the substance to be cooled. As the liquid refrigerant boils, it soaks up large amounts of latent heat.
In my H.E.A.T. Machine technology the evaporator is or is incorporated into my boiler.
Compressor: In order to remove the “hot” (boiled) gasses from the evaporator, ordinary refrigeration systems use a compressor. When the “hot” gasses are compressed, they rise in temperature according to Boyles Law. They also rise in pressure, which raises the boiling point, so the gasses don’t have to lose as much temperature before they will condense.
Condenser: The condenser is the heat exchanger that allows the heat from the compressed “hot” gasses to leave the refrigerant and go out into the surrounding (cooler) environment, like your kitchen. That would be an air cooled condenser. You can cool condensers with liquid or solids as well.
In my H.E.A.T. Machine technology, there is no condenser as such; the gasses have the heat taken out of them by doing mechanical work.
The condensed refrigerant drains (or is pumped) from the condenser into a storage reservoir where it waits its next chance at the evaporator.
Expansion valve: Sometimes is a simple orifice, the expansion device allows only enough refrigerant into the evaporator for what the compressor removes, thus keeping the maximum boiling action going on. At least until the cooling system has done its job.
Generally speaking, my H.E.A.T. Machine technology replaces the expansion valve with a turbine. There is a company called Creative Energy Systems, in Edmonton, Alberta, Canada, that uses this concept to advantage. They recognized that the pressure reducing valves on high pressure gas pipelines could be replaced with turbines. In this manner they get the pressure drop (across the turbine) required to operate their appliances and recover some of the energy that was expended in pressureizing the gas. This works because the turbine converts the heat energy in the gas to mechanical energy. The result is a cooler gas coming out of the turbine. The cooler gas has less volume, therefor less pressure.
In order to understand the H.E.A.T. Machine, you will also have to understand what is known as the GAS LAWS. I will give you a preview here so you can look them up in your physics books to more completely understand them. For example terms like “atmosphere”, “mole”, and “oK”. They are not hard but you need a gut feeling for them or you may not understand some of the H.E.A.T. Machine design concepts. You will also want to get familier with various conversion tables because data that you find may be metric.
Perfect Gas Law: PV = nRT
P = Pressure in atmospheres
V = Volume in liters
n = number of moles
R = Gas constant (0.0821 liter-atmospheres/oK/mole.
T = Temperature in degrees K
If constant pressure, V1/V2 = T1/T2
If constant temperature, P1/P2 = V2/V1
If constant volume, P1/P2 = T1/T2
Of course in real life nothing is constant, so the real answer usually involves a combination of the above.
Boyle’s Law:
If temperature is kept constant, the volume of a given mass of gas (mole) is inversely proportional to the pressure which is exerted upon it.
Initial Pressure = Pressure Change
Initial Volume Volume Change
Charles’s Law:
If pressure is kept constant, the volume of a given mass of gas is inversely proportional to the pressure which is exerted upon it.
InitiaI Volume = Volume Change
Initial Temp. oK Final Temp. oK
There are more Gas Laws but these are the most applicable.
Work is defined as a force moving through a distance. One foot-pound (ft-lb) is one pound moving through a distance of one foot.
Heat is the energy that is transfered between two regions because of a difference in their temperatures.
Bibliography
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I wish to extend a special thanks to the International Tesla Society for having me as a guest speaker and for all the little ways they support alternative energy technology, particularly technology that applies the work of Nikola Tesla.
The International Tesla Society has now been disbanded.
