FR2538510A1 - Method and device for integrated thermodynamic heating with a small pressure difference - Google Patents

Abstract

The invention relates to a heating method, via a heat pump, with small differences in pressures and temperatures obtained by the association of the embedded evaporation method and of condensation distributed throughout a heating layer. The condenser is produced on site in the form of a heating layer consisting of elements welded in parallel to two or more collectors linked to the condensate output and return lines. The head losses in this condenser are low compared to the pressure difference due to 1 DEG C temperature difference. This makes it possible to use elementary lengths having a tolerance of 30 %, and moreover generates a spontaneous inflow of vapour towards the most thermally loaded sections. The evaporation method is called "embedded". Usually reserved for large installations, this method allows, by the use of specific material, the difference between the temperature of the external heat energy and the temperature of the saturated in-drawn vapour to be diminished. An auxiliary evaporator is used for separating dissolved oil and directing it towards the main aspiration line. The cold water network is fed by a centrifugal pump and comprises, besides the evaporator, two columns descending into two wells which are 20 to 40 metres apart. The pumping column and the output column do not have a foot valve, and the entire circuit is evacuated of air in such a fashion as to relieve the pump of its lifting work and to lessen its impact on the performance coefficient of the installation.

Description

 The present invention is intended to heat various premises by the technique of heated floors with the essential aim of high energy efficiency.

 Current heat pumps, manufactured in the factory and therefore in power ranges, are devices with mechanical eomp - ession of condensable vapors operating by removing external calories transferred to an auxiliary transport fluid in the form of sensible heat. The temperature at which this transport fluid operates depends on the process of emission of calories. It is maximum, and of the order of 550C for emission by radiators in an undisturbed or mixed installation. It is minimal and of the order of 3000 for the heating layers on the ground. These temperature differences do not affect the efficiency of combustion boilers. In the case of a heat pump where the pressure of hot gases is closely linked to their temperature, the efficiency or coefficient of performance of the installation changes very quickly by increasing the eclectic energy consumption of the compressors.

 For the purpose of adapting to a maximum of cases of heat distribution networks, the dimensions of the hot exchanger, or condenser, are provided for use at 55 C. At the pressure corresponding to this temperature, the gases hot, very dense, find / a passage and a sufficient condensing surface. The same mass flow rate of lukewarm gases in the same eondenseuz cannot be effected at a pressure sufficient to heat es to 30 ° C., the expanded gases having neither sufficient passage nor collation surface. temperature 69 therefore rise, because of the pressure drops and the thermal gradient of the boundary layers of the condensate, to a new equilibrium, little different from the previous conditions, therefore the efficiency of the installation also varies little.

 In the current state of the art and of the market, the investment in larger exchangers would prohibitively increase the cost of an installation combining expensive technology and a conventional hot water distribution network.

 The investment would be further burdened by the need to split the equipment because of the heavy weight @ op for the current network of installers.

 @@ mpes with current heat take the calories outside either on the air, sit on ground water. In all cases, this involves evaporating a fluorocarbon fluid in an o @ gane called an evaporator. This evaporator is supplied with expanded liquid fluid at a pressure comparable to the suction pressure of the compressor. The supply is made either by a regulator which is an automatic valve, or by a throttle materialized by a tube of small section called capillary.

 In both cases out the fluid entering da @ s the evaporator but in contact with the walls heated by the external calories, and leaving the evaporator in the form of gas. The weight of liquid by successive elements of length is therefore decreasing by following the current. It follows that the heterogeneous mixture contained in the evaporator offers less and less contact surface between the liquid part and the walls.

 The pressure of the gases at their outlet from the evaporator is in relation to their temperature such that no drop of liquid can remain under pain of damaging the compressor. Evaporation is said to be dry. Two conflicting interests are at stake. protect the compressor and extract the densest vapor possible. The balance weighs on the safety side at the expense of performance, especially with the use of a capillary.

Current compressors are piston and cylinder. Very robust, these materials consume more energy for their own movement than compressors with rolling pistons and pallets
All heat breaks have a performance coefficient closely related to the difference between suction and delivery.

(of "The heat pump - volume 1 by Bernier - ed. PYC)
the current performance coefficients are between 1.5 and 4, that is to say that the share of "free" energy represents from half to three times the share of energy consumed.

 The object of the present invention is to reduce the pressure and temperature differences between the discharge side and the suction side of the heat pump, without any additional cost of the installation.

 It consists in using the internal surface of the pipes embedded in the heated floors as a condensing surface.

The surface temperature of a heated floor must be as homogeneous as possible, to avoid areas of discomfort requires a pitch of piping from 0.15 to 0.30 meters depending on the orientation of the rooms. Its medically recommended maximum is 260C.

 The use of condensable vapors, by their spontaneous influx towards the most thermally charged sections, namely the coldest sections, allows an installation at constant density of pipes per unit area1 unlike installations with heat transfer fluid with sensitive heat. In these latter, the viscosity and the flow rate of the fluid are not influenced by its operating temperatures.

 the large dimensions of the distributed condenser considerably reduce the pressure losses and the thermal gradient of the boundary layer of the condensers.

 On a test platform, a condensing temperature of 270C provides a floor surface temperature of 230C, sufficient to meet the heating needs of 85% of the heating period. For conditions of -5 C outside and +19 C inside, the condensation temperature is 320C.

 The present invention uses the technique of flooded evaporation, usually reserved for high power refrigeration installations. use is also made of a small auxiliary evaporator with dry evaporation intended to bring back to the casing of the compressor the oil which passes through the oil separator in the form of mist and vapor and diffuses dan6 the circuit.

 The use of flooded evaporators, unlike the use of dry evaporators allows to obtain a suction pressure much closer to the temperature of the source of external calories. This is because the surfaces involved are not the same, and because the flooded evaporator is traversed by a stream of liquid containing vapor bubbles. The exchange surface between the liquid part of the fluid and the wall is therefore more grade.

 At the outlet of the evaporator, a separating bottle makes it possible to suck only vapors. The separated liquid part returns to the evaporator by gravity and distributes by stirring the oil concentration within the mass of liquid fluid.

 This technique causes saturated and not superheated vapors to be sucked in, increases the density and the flow rate of the sucked vapors and reduces the superheating of the discharged gases by reducing the compression ratio.

 On a test platform a water temperature of 14 C allows to evaporate at 12 C.

The use of rotary piston and paddle compressors, which consume less energy than reciprocating piston compressors, is particularly suitable for these operating conditions.
The present invention, intended to supply heating needs alone, with an investment comparable to that of a conventional central heating with liquid fuel, operates with a performance coefficient of between 6 and 8 depending on the type of compressor used. Particularly intended for new homes, this process can be used in rehabilitation.

 The installation is presented in three parts, which are: the heating layer, the evaporator group and the source of external calories.

 The heating layer is made up of forty tubular condensing circuits of 10 mm useful diameter and 12 to 15 meters maximum length, for a typical surface of 110 square meters.

The pressure drop in the elementary circuits being much less than the difference in gas pressure due to a degree of temperature difference allows a tolerance of 30Xo over the length of the elements. These elementary lengths are neither welded nor terminated in their part embedded in the chaBeO the inputs of these elementary circuits are welded to one or two hot gas distributors.

The outlets are welded to one or two condensate collars.

The hot gas distributor (s) are connected to the oil separator by a seamless submerged pipe, 24 mm in diameter.

The condensed fluid collector (s) are connected to the liquid reserve by a seamless submerged pipe of 16 mm of useful dimmeter. These collectors are preferably located in masonry niches closed by an access door ventilated by a low grille opening onto the outside. Collesters and elementary feeders are insulated All of this part of the installation is made up of "cold" quality tubes brazed with silver. It is subjected to a pressure test and sealing by fluorocarbon liquid before and during the installation of the aggregate. The tubes are fixed with the usual precautions.

 The evaporator group is preferably in a built-in niche located in a service room and opening onto the outside by a door fitted with a ventilation and a key This group is assembled in the workshop and its outputs are made by metal vibration dampers. It includes the main evaporator on which the compressor (s) are fixed, the suction separation bottle, the oil separator, the auxiliary evaporator at the bottom, the constant level supply valve, the reserve liquid, the safety devices and a multi-pin connector intended to connect the 11 chest of drawers located inside the room.

 The auxiliary evaporator is heated by the liquid returning from the installation. It is a coaxial evaporator with dry expansion fed by gravity from the main evaporator through a manual control valve, a solenoid valve, and a filter drier which can be isolated. Its low outlet joins the lower part of a stick joining the suction of the separating bottle to the suction of the compressor. The oil leaving it is brought back to the compressor by the main flow.

 Auxiliary evaporation represents 2 to 5% of the main evaporation.

 The source of external calories is groundwater or spring water. As far as possible, two boreholes 20 to 40 meters apart are used, one for drawing water and the other for discharging water. This circuit is under vacuum so as to use the fall of the downcomer to relieve the pump of its lifting work. the draw-off and rejection columns have no check valve, the priming of the circuit being done by suction of air at the first commissioning.

The pump returns to the evaporator. The evaporator water circuit is made of a single metal to prevent corrosion by galvanic couple.

On the test platform, the equipment used, apart from the compressor and the oil separator, does not exist in current production. It was necessary to adapt existing equipment to new functions. The evaporator is in fact a multitubular condenser with tubes with laminated fins and internal water circulation (9 RQ 15 - The refrigeration compressor)
This evaporator with flooded tubes is surmounted by a separation bottle allowing, by decantation and speed reduction, to suck in the upper part only the saturated vapors. the liquid parts from the evaporator return to the lower part by gravity, via a tube of 22 mm in diameter. The liquid reserve has a capacity of 8 liters. The level is maintained by a constant level valve located at the end of the evaporator. Several indicators allow the operation of the system to be observed, namely ç an indicator on the return of the oil separator, two opposite on the suction bottle one at the outlet of the auxiliary evaporator. The oil bath is permanently heated to avoid dilution. The compressor is a BITZER BHS 191 with pistons and cylinders. The coefficient of performance of the test is greater than 6.

Claims (5)

 I) Method of thermodynamic heating with mechanical compression of condensable vapors characterized in that it is integrated into the building and provides 6 to 9 times more energy than it consumes, by reducing the difference in pres - characteristic features.  2) Device according to claim I, characterized in that it uses the inner surface of tubing networks embedded in the floor screeds as a condensing surface of condensable fluids  3) Device according to claims I and 2 characterized by the fact that it allows-to achieve heated floors with a single density of tubes per unit area, whatever the characteristics of the rooms, thanks to the propensity of steam to condense on the coldest surfaces, the pressure drops being much less than the pressure difference resulting from a temperature difference of I C.  4) Device according to claims 2 and 3 characterized in that it allows-to use networks of unequal lengths of 30%.  5) Device according to claims I and 2 characterized in that it p @ r- -met to tighten the pressure gap by a wet type evaporation