WO2011028186A2

WO2011028186A2 - Residential thermal solar chiller

Info

Publication number: WO2011028186A2
Application number: PCT/SI2010/000049
Authority: WO
Inventors: Marko Matkovic
Original assignee: Marko Matkovic
Priority date: 2009-09-04
Filing date: 2010-09-03
Publication date: 2011-03-10
Also published as: WO2011028186A3

Abstract

This invention, residential thermal solar chiller, relates to a compact absorption cooling unit that is easily manufactured and assembled and has moderate nominal cooling power (up to 10 kW). The use of machine is dedicated but not limited to cooling and air-conditioning of smaller dwellings by the use of thermal solar energy. It is a single effect absorption unit with LiBr-Water working medium, which enables operation at rather low desorption temperature, hence the adoption of the flat plate collectors as a heat source is feasible. The chiller is axially symmetrical in the shape of a cylinder with convex top and convex bottom. The hermetic sealing of the chiller's outer shell is realized exclusively on the contact of the body's outer shell (7) with the convex head's outer shell (5) and with the convex bottom shell (8). Due to the water cooled absorber and condenser; the chiller can be installed within the thermal envelope of the building. Its size is comparable to a domestic fridge, which facilitates transport and installation of the chiller within the building.

Description

RESIDENTIAL THERMAL SOLAR CHILLER

This invention relates to a residential thermal solar chiller (chiller) namely driven with the thermal solar energy. It is suitable for heating, cooling and air-conditioning of buildings. The water cooled chiller is small size (up to 10 kW) single effect LiBr-water absorption machine that is fed with low temperature heat source.

The technical problem solved with the invention is a kind of a construction, which:

- forms with a casing (shell) in the shape of a cylinder with convex top and convex bottom a single volume thou divided with pressure basin in high pressure and low pressure sections. The casing is used to separate the internal volume from surrounding gases at ambient pressure,

- connects high pressure and low pressure sections with a service column set along the center axis of the machine,

- has a condenser in the shape of a thick wall irregular hemisphere set in the high pressure section just beneath the convex head's outer shell that can also serve as an extended condenser's heat transfer surface. Desorber (generator) is set below the condenser in the middle. In the low pressure section around the service column (that can also be used as an extended heat transfer surface area of an evaporator) there is an evaporator installed and surrounded by an absorber set just beneath the cylindrical body's outer shell that can serve as an extended heat and mass transfer surface of an absorber as well,

- has a drainage system of the condensate placed in the cavity between the generator and the condenser while it has a separator of drops inserted in the layer between the evaporator and the absorber,

- employs a tube-in-tube heat exchanger in the form of a conic helix, for internal heat exchange between the strong solution from generator and rich solution from absorber, embedded in the cavity between the pressure basin and the bottom of the generator,

- enables solving eventual complications due to crystallization of salt in the following three ways:

1 ) by controlling the saturation temperatures and the temperatures of a secondary fluids in all heat and mass exchangers,

2) by circulating the excess of a hot solution from the generator through the external annulus of a tube-in-tube heat exchanger back into the generator in order to increase the solubility of a strong solution from the generator,

3) internal heat exchanger and distribution nozzles on the side of a strong solution are realized so as to disable accumulation of a crystals and hence to disable chocking, - with adoption of a thermostatic valves without the use of external energy disables distribution of a hot solution into absorber,

- enables realization of a compact machine, simple manufacturing of a construction elements and simple assembly, which enables serial production with significantly decreased production costs that makes the chiller economically attractive product as well.

There are several known Lithium Bromide - water absorption chillers with comparable cooling power. However, they all have rather complex external geometry in terms of more structured accommodation of heat and mass exchangers within the chiller, which makes the hermetic sealing more difficult. They are also distinguished by different flow patterns. Manufacturing and assembly of construction elements is either technologically more complex, which makes the product more expensive and less reliable, or the temperature regimes and the size of machine do not allow the implementation of such chillers into small size HVAC systems. Some products were developed with integrated air cooled absorbers and condensers that requires the installation of such chillers outside the thermal envelope of the building.

Unresolved problem remains the construction of a compact and reliable residential solar chiller with moderate cooling power (up to 10 kW) and still economically attractive investment. The invention solves the problem with the residential thermal solar chiller with a service column in the center and a casing in the form of a cylinder with a convex top and bottom; the casing, which can also present the extended heat and mass transfer surface of a condenser and absorber. The invention will be described on the realization case and picture that shows:

Fig. 1 residential thermal solar chiller according to invention in an axonometric projection

Head takes part of a high pressure section installed above the body of a chiller, which includes the low pressure section set on the base 21. The head is located between the pressure basin 6 and the convex head's outer shell 5 of a chiller, while body involves the elements within the bottom shell 8, body's outer shell 7 and pressure basin 6. The chiller is externally insulated 22, 23 with the exception of the base and the bottom shell.

Head comprises of a desorber 2 (generator), drainage system of the condensate 14, condenser 1 in the shape of a thick wall regular or irregular hemisphere, collector of the condensate 9, desorber's bottom 10 and intermediate cavity 16 between the pressure basin 6, collector of the condensate 9 and desorber's bottom 10. The intermediate cavity 16 accommodates a co-axial heat exchanger assembly in the form of a conic helix used for internal heat exchange. In the cavity beneath the pressure basin a thermostatic valve is installed that prevents high temperature solution from being pumped into the absorber. On the top end of the head's outer shell 5 there are heating and cooling water ports (18 and 17) set for feeding the generator and the condenser respectively. There is a free falling film type evaporator 3 placed around the service column 13 within the body. It is surrounded by separator of drops 15 and by absorber 4 placed beneath the body's outer shell 7. Body ends up with refrigerant collector 11 on the bottom that closes with convex bottom shell 8. The evaporator's cooled water ports 19 and the absorber's cooling water ports 20 are taken out through the bottom shell 8 to the outer surface of the base 21.

There are namely two pumps installed within the base 21. The first one is used to circulate refrigerant within the low pressure section whereas, the second one is installed to circulate strong solution through absorber 4 and to pump enriched solution into generator 2. The alternative version of pumping the refrigerant can have the pump installed in the refrigerant collector 11 beneath the evaporator 3. Such solution, which requires the installation of only one pump within the base - at ambient pressure, simplifies issues related to sealing difficulties and pumping at low pressure.

The head's outer shell 5 has in the center an assembly jar 24 that serves for accommodation of desorber's heating water ports 18 and condenser's cooling water ports 17. The head's outer shell 5 is preferentially made of a single steel sheet. Materials as well as manufacturing techniques of the head's outer shell 5 can be different; however, the chiller must obey high requirements of tightness under low pressure. Nevertheless, the realization of the head's outer shell 5 without the assembly jar 24 in the center is also possible. In that case the desorber's heating water ports 18 and the condenser's cooling water ports 17 are realized anywhere on the head's outer shell 5.

The condenser in the shape of a thick wall hemisphere 1 is attached underneath the head's outer shell 5 while the drainage system of the condensate 1 is set beneath the condenser in order to drainage the condensate into the collector of the condensate 9.

The drainage system of the condensate 14 is made of any number of conical rings, scales or tiles with low optical emissivity and absorptivity. Elements are made from materials with low thermal conductivity as well and they can be arranged in different layers. The arrangement of the elements is favorable to an effective drainage of the condensate from either side of the elements into the collector of the condensate 9, while causing minimum pressure loss due to the vapor flow from the desorber into the condenser If conical rings are applied, they can be slightly folded downward and upward on the external and internal perimeter respectively. The tilt of the adopted elements from chosen materials and hence given surface tension at given temperature is such that the condensate from the entire bottom surface successfully flows onto the external side of the drainage system 14 and from there into the collector of the condensate 9. There is another important function of the drainage system of the condensate 14. It is associated to the irradiative insulation between the generator 2 and the overhead condenser 1. Materials used and surface treatment of the drainage system 14 enables both good drainage performance and good irradiative insulation properties from the long wave radiation. Any heat exchange between the generator 2 and the condenser 1 as well as any leakage of the condensate back into generator is associated to lower efficiency; therefore, lower COP would be expected unless the described solutions were taken into consideration.

The desorber 2 is set in the middle of the head. Relatively large volume occupied by the desorber within the high pressure section is due to a desired amount of vapor generation at minimum required wall to saturation temperature difference

Desorber's bottom 10 and collector of the condensate 9 are preferably made from a single peace. Basically, there are two vessels in contact manufactured so as to offer minimum possible heat transfer between them. The first vessel is used to collect strong solution from the generator, while the second vessel, which forms the channel around the edge of the first one, is set to collect the condensate. If the two vessels were made separately, the perfect sealing between the two peaces should be ensured. However, the hermetic coupling either by soldering or by bonding should also be ensured between the collector of the condensate 9 and a pressure basin 6. In this way the accumulation of the refrigerant and salt in the intermediate cavity 16 is avoided, while structure gains additional rigidity.

A pressure basin 6 is preferentially made by steel sheet forming technique. The elements: pressure basin 6, reflector 25 and service column 13 are arranged within the chiller so as to give to the machine additional rigidity and armature for internal infrastructure arrangement, which needs to be assembled before the junction of the head and body of the machine. The hermetic sealing must be ensured between the pressure basin 6 and the body's outer shell 7 in order to prevent the vapor refrigerant leakage into the lower pressure section resulting in faulty operation of the machine.

The service column 13 is in the upper part attached, preferably welded onto the reflector 25, while it is hermetically joined with refrigerant collector 11 on the bottom end.

There is a free falling film type evaporator (evaporator 13) adopted within the machine, which operates at almost constant saturation pressure during evaporation thus the constant evaporation temperature is ensured over entire evaporator. It is arranged around the service column 13 above the refrigerant collector 11. The evaporator's cooled water ports 19 are taken out through the bottom shell 8 on the base 21.

The absorber 4 is installed beneath the body's outer shell 7 around the separator of drops 15. The absorber's cooling water ports 20 are taken out through the bottom shell 8 on the base 21.

The refrigerant collector 11 is set on a salver on the bottom shell 8. Around the perimeter of the refrigerant collector 11 the separator of drops 15 is arranged over entire height among the evaporator 3 and the absorber 4. The hermetic sealing must be ensured between the bottom shell 8 and the body's outer shell 7 in place where rich solution collector 12 is arranged. The use of separator of drops 15 is analogical to the one by drainage system of the condensate 14; hence it prevents liquid migration in both directions between the evaporator 3 and the absorber 4. Another functionality of the separator of drops 15 is attributed to a long wave irradiative insulation between the two heat and mass transfer elements. Since the saturation pressure within the low pressure section (evaporator, absorber) is in the order of magnitude lower with respect to the high pressure section (generator, condenser), particular attention has been paid to design the efficient separator of drops 15 with lowest possible pressure drop during refrigerant vapor flow.

The body's outer shell 7, the head's outer shell 5 and the bottom shell 8 keep the machine hermetically sealed. There is an edge folded outward - flange, on the top and the bottom end of the body's outer shell 7. They are used to realize the hermetic sealing between the head's outer shell 5 and the bottom shell 8, while improving the radial rigidity of the machine.

All elements, particularly heat and mass exchangers are planned so as to reach the nominal cooling power at specified test conditions.

Claims

1. Residential thermal solar chiller, wherein

the body's outer shell (7) in the shape of a cylinder has the edges on the top and on the bottom folded outward - flanges, convex head's outer shell (5) and convex bottom shell (8).

2. The device of claim 1 , wherein

the condenser (1 ) is set in a thick layer just beneath the convex head's outer shell (5), below the condenser the drainage system of the condensate (14) surrounded with the collector of the condensate (9) beneath and the generator (2) with the desorber's bottom (10) in the middle below the drainage system.

3. The device of claim 1 , wherein

the evaporator (3) in a shape of a hollow cylinder is installed around the service column (13), which can also serve as an extended evaporator's heat transfer surface area, just beneath the body's outer shell (7) around its entire perimeter the absorber (4) takes place and the separator of drops (15) is set in the cavity between the evaporator (3) and the absorber (4).

4. The device of claim 1 , wherein

the machine's outer shell with: head's outer shell (5), body's outer shell (7) and the bottom shell (8) represents additional heat and mass transfer wall surface area of the condenser and absorber due to a good thermal contact between the condenser (1) and the head's outer shell (5) and good thermal contact between the absorber (4) and the body's outer shell (7).

5. The device of claim 1 , wherein

the drainage system of the condensate (14) comprises of any number of conical rings, scales or tiles with low optical absorptivity and emissivity, which are arranged so as to enable an effective drainage of the condensate from either side of the elements into the collector of the condensate (9), while causing minimum pressure loss due to the vapor flow from the generator into the condenser.

6. The device of claim 1 , wherein

the separator of drops (15) comprises of any number of bended strips with low optical absorptivity and emissivity, which are arranged so as to prevent liquid migration in both directions between the evaporator (3) and the absorber (4) while causing minimum pressure loss due to vapor flow from the evaporator into the absorber.

7. The device of claim 1 , wherein

the hermetic sealing of the chiller's outer shell is realized exclusively on the contact of the body's outer shell (7) with the convex head's outer shell (5) and with the convex bottom shell (8).

8. The device of claim 1 , wherein

the desorber's heating water ports (18) and the condenser's cooling water ports (17) are installed on the top in the middle of the head's outer shell (5), while absorber's cooling water ports (20) and evaporator's cooled water ports (19) are installed on the bottom.

9. The device of claim 1 , wherein

all comprising elements: head's outer shell (5), condenser (1), drainage system of the condensate (14), desorber (2), collector of the condensate (9), desorber's bottom (10), pressure basin (6), service column (13), evaporator (3), separator of drops (15), absorber (4), refrigerant collector (11), rich solution collector (12) and bottom shell (8) are axially symmetrical and lined up with machine's axis while slight deviation from axial symmetry or alignment of the elements: collector of the condensate (9), refrigerant collector (11) and rich solution collector (12) is kept in order to make collection of the liquid refrigerant and solution easier.