DE10224924A1 - Method for increasing or reducing temperatures has refrigeration system with twin piston compressor and double condensers - Google Patents

Abstract

A fan (3) blows air over the evaporator (2) and one part of the condenser (5a) the other part (5b) of which is cooled by ambient air. The compressor (4) has two pistons (8) on a common drive rod (9) which suck cold vapour through valves from the evaporator and transfer it to the condenser through automatically operated valves (13). The variable volume spaces (14) behind the pistons are interconnected and also lead to the condenser (5b) which is used to drive the pistons. The evaporator provides condensed water collected which may be drained off.

Description

The invention relates to a method to generate usable heat or cold by means of a heat or cooling process according to the preamble of claim 1. Furthermore, the invention relates a device according to the preamble of claim 10.

For generating usable heat for heating purposes is about the evaporator thermal energy of any origin and added via the capacitor on one higher Temperature level given to the consumer.

To generate usable cold, the Evaporator one to be cooled Medium thermal energy withdrawn and over the condenser thermal energy released to the environment.

An important application for such a Process is water extraction from the air in arid areas of the world Earth. The water supply for the population is a key problem here represents.

In the known method is for compression of the refrigerant a big Drive power required. As a result, high investment and Operating costs, the application of the process for water extraction make it uneconomical from air.

Accordingly, the invention is the Task based on providing a remedy here and a possibility to create that for the external drive power required to drive the compressor to minimize.

This task is accomplished through a process solved with the features of claim 1.

The drive power is reduced by the work on the drive obtained with the aid of the drive medium the piston is used. As a drive medium, for example Nitrogen can be used. The memory can be any pressure vessel. The pressure of the drive medium must be at least the pressure in the condenser correspond.

The capacitor preferably forms the store being the refrigerant is used as the drive medium. Thus the sum of the rooms in the Cylinders behind the pistons, in the supply lines and the condenser converted into a pressure storage system. The effort at external Energy is generated by using the pressure volume work from the condenser lowered, which also acts on the pistons and thereby the otherwise unused evaporation work from the Evaporator in the expansion process in the process and makes usable.

Compared to the classic formula (2), the formula (1) represents the additional power (-P _S V _A ) from the evaporation for the technical work of a single-piston or turbo compressor. L = -P S V A + [(P S V A ) / (κ - 1)] [(P k / P S ) [(Κ-1) / (κ)] - 1] (1) A = + κ [(P S V Z ) / (κ - 1)] [(P k / P S ) [(Κ-1) / (κ)] - 1] (2) in which
L = output (per hour)
A = work (per piston stroke)
P _S = low pressure or suction pressure
P _k = high pressure or condensation pressure
κ = isentropic exponent of the refrigerant
V _A = vapor volume of the refrigerant circulating in one hour at low pressure or suction pressure
V _Z = cylinder volume To extract water from the air, it is drawn in from the surroundings by a blower and passed through the evaporator in such a way that water is separated from the air.

With the help of formula (1), the optimal one can be selected from the various available refrigerants. The aim is to achieve the highest possible temperature difference between refrigerant vapor at P _k and outside air. This ensures that a condenser system with the smallest possible exchange surface for the respective cooling air can be used, which results in a small size of the unit and low air fan output.

Preferably, the speed of the blower dependent on on the temperature of the refrigerant regulated in the evaporator. about the regulated volume flow of the moist air takes place with a constant enthalpy, even with changing temperatures and humidity levels in the air. This means that the same cooling capacity can always be achieved of the evaporator and thus the full system output can be used. Alternatively, it is also possible the speed depending to regulate the enthalpy from the air temperature and the relative humidity can be calculated.

An advantageous embodiment of the Invention is that the exiting from the evaporator cold, dry air led to the condenser and in the condenser in heat exchange with the refrigerant brought. This way it takes over the cold air is part of the cooling of refrigerant vapor.

Preferably, the air in the condenser Counterflow to the refrigerant guided, which leads to high efficiencies.

For Obtaining water from the air may require that refrigerant additionally in a second condenser in heat exchange with the ambient air brought.

For this application is an advantageous development that the liquefied refrigerant throttled by means of a capillary before entering the evaporator becomes. This enables a constant flow. At constant evaporator pressure a pressure swing avoided. As a result, interference is avoided.

Since the need for drive power is extremely low, the invention offers the advantageous possibility that the power supply by means of a photo voltaic system takes place. It is particularly advantageous that the number of solar cells can be kept low.

The invention also provides one Device, in particular for performing the method according to agreement 1, with a piston compressor that has at least one cylinder has a piston, characterized in that the piston with its back delimits a substantially closed space in the cylinder, which has a Line to a store for one under elevated Pressurized drive medium is connected.

The required external drive energy for the Piston compressor is very small in the device according to the invention. This opens up in addition to the use in the method according to the invention, further possible uses. Since the structure is simple, the investment costs are relatively low.

A particularly advantageous further development exists in that the piston compressor has two cylinders, each with a piston has, which are coupled together and are moved in opposite or parallel directions can. In the cylinders there is a space behind each piston, its volume either gets smaller or bigger and so together with the storage volume constant with regard to pressure , Temperature and volume remain and thus do not give off any enthalpy.

The piston compressor is advantageously also used two cylinders in axial design.

The invention is explained below of a preferred embodiment of the method according to the invention and the device in connection with the drawing.

• 1 eine schematische Darstellung des erfindungsgemäßen Verfahrens und der Vorrichtung;
• 2 das Verfahren in einem Druck – Enthalpie-Diagramm bei isentroper oder adiabater Fahrweise.

The drawing shows in:

• 1 a schematic representation of the inventive method and the device;
• 2 the procedure in a pressure - enthalpy diagram for isentropic or adiabatic driving.

In 1 schematically shows a method for extracting water from air in arid regions of the earth.

In a closed pipe system 1 circulates a refrigerant, usually a fluorocarbon. In an evaporator 2 there is a heat exchange with the ambient air by means of a fan 3 is sucked in. This condenses water that is drained off. The evaporated refrigerant is from a piston compressor 4 sucked in and compressed to a higher pressure. This increases the temperature of the refrigerant vapor. The hot steam is in two condensers 5a and 5b cooled and condensed. Using a capillary 6 the liquefied refrigerant is expanded. At lower pressure, it flows back into the evaporator 2 , The capacitor 5a is by means of an air line 10 the one on the evaporator 2 escaping cold dry air supplied. The condenser 5b is cooled with ambient air.

The piston compressor shown schematically 4 has two cylinders 7 with two pistons 8th on that in a known manner by means of a piston rod 9 with a drive, not shown, for example an electric motor or a gas engine, are moved back and forth. The pistons 8th work, e.g. B. offset by a flywheel, in opposite directions, that is, at the same time opposite processes in the two cylinders. Every cylinder 7 has a low pressure connection 11 and a high pressure connection 12 for the refrigerant to be sucked in or compressed. The connections 11 . 12 are in a known manner with automatically opening and closing valves 13 Mistake. Every cylinder 7 is closed at the end except for the bushing for the piston rod, so that each piston 8th with its back a volume-changing room 14 limited by an open line 15 with the capacitor 5b communicates. In this way, the refrigerant under increased pressure is used to drive the pistons and thus the external drive energy is reduced.

Another advantage of using the refrigerant as the drive medium is that it can also be used at higher pressure levels and thus temperature levels in the condenser 5 , Therefore, the use of the outside air is also possible in hot areas for cooling and condensing the refrigerant vapor, which gives the process flexibility.

Faults in the system are caused by Pressure - and Suction valves that are adapted to a driving style, in which also condensate can be avoided. The adiabatic driving style reduces the energy requirement, so that use in the wet steam area is conceivable.

In 2 the process is shown in a Mollierian log (p / h) diagram. The calculation of the external drive power for the compressor depends on the type of refrigerant and the meteorological conditions. For a system with a water separation of 3000 l per day, the demand fluctuates by about 10 KW installed capacity, e.g. B. calculated a solar system to 24h in sunny areas.

The cooling requirement and thus the amount of refrigerant is calculated from the air temperature and humidity, and from it the necessary Condensing pressure.

According to 2 the refrigerant is drawn in by the compressor with the condition marked with 1 and to the condition 2 '' (instead of 2 on isentroper or on 2 ' with adiabatic driving style). The leading to 2 "indicate that there may be a change in performance depending on the refrigerant and / or the air temperature. The compressed, heated refrigerant is in the condenser at constant pressure on the condition 3 cooled and then to the state 4 ent stressed. How out 2 after the expansion, the refrigerant is in the wet steam area and has cooled down to a temperature of, for example, -10 ° C. In the evaporator, the heat is exchanged with the ambient air, whereby the refrigerant is brought to the initial state marked with 1.

The performance of the process for water extraction depends on the dimensions of the compressor, the evaporator and the condenser as well as the meteorological conditions, so that the results of a calculation are given here only as examples:
3000 liters of water are extracted from 300,000 cubic meters of air in a 24-hour day. The pressure difference that occurs on both sides of the piston causes a suction, which once does work to provide the necessary work in the opposite stroke to overcome the suction. When using the working formulas for the calculation of the pressure volume work, with adiabatic (enthalpy H _{2 '} - enthalpy H ₁ ) or isentropic guidance, the difference results in the work still to be done, which together with the work to overcome the friction loss of the piston movement and the flow energy in the tubes and the energy loss from the air flow in the evaporator results in a power requirement of about 5 KW per day through solar energy cells. From this follows the requirement of a power reserve by solar energy cells of approx. 5 KW via battery storage for post-operation.

Efficiency of the drive motors, Power losses when loading and unloading the electrical storage batteries and crank losses are factored in, on the other hand reserves for operation in the overheated Refrigerant vapor not yet, they are considered minor in this process.

Within the scope of the invention are without further variation options given. The piston compressor can be of any design accomplished become.

Claims (12)

Method for generating usable heat or cold by means of a heating or cooling process, comprising the steps of - evaporating a refrigerant in an evaporator, - drawing in and compressing the refrigerant by means of a piston compressor which has at least one cylinder with a piston which moves by means of a drive is, - liquefying the gaseous refrigerant in a condenser, - throttling the liquefied refrigerant for re-evaporation in the evaporator, characterized in that when compressing a pressurized drive medium from a reservoir into a substantially closed volume-changing space in the cylinder behind the piston flows in and flows back into the reservoir when it is sucked in. A method according to claim 1, characterized in that the Condenser forms the storage and that the refrigerant as the drive medium is used. A method according to claim 1 or 2, characterized in that the evaporator with air as the heat exchange medium is applied so that water is separated from the air the air is drawn in from the surroundings by means of a blower becomes. A method according to claim 3, characterized in that the Fan speed dependent on on the temperature of the refrigerant is regulated in the evaporator. A method according to claim 3 or 4, characterized in that the cold, dry air emerging from the evaporator to the condenser guided and in the condenser in heat exchange with the refrigerant brought. A method according to claim 5, characterized in that the Air in the condenser is directed in counterflow to the refrigerant. Method according to one of claims 1 to 6, characterized in that that the refrigerant in a second condenser in heat exchange with the ambient air brought. Method according to one of claims 1 to 7, characterized in that that the liquefied refrigerant throttled by means of a capillary before entering the evaporator becomes. Method according to one of claims 1 to 8, characterized in that that the power supply to the electrical consumers by means of a Photovoltaic system takes place, which has an electricity storage. Device, in particular for performing the method according to one of claims 1 to 9, with a piston compressor ( 4 ) that has at least one cylinder ( 7 ) with a piston ( 8th ), characterized in that the piston ( 8th ) with its rear side an essentially closed space ( 14 ) in the cylinder, which is connected via a line ( 15 ) to a memory ( 5 ) is connected for a drive medium under increased pressure. Apparatus according to claim 10, characterized in that the piston compressor ( 4 ) two cy linder ( 7 ) with one piston each ( 8th ) which are coupled to one another and are moved in opposite or opposite directions. Device according to one of claims 10 or 11, characterized in that the piston compressor ( 4 ) has an axial design.