FORM - 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
PROVISIONAL
Specification
(See section 10 and rule 13)
REFRIGERATING SYSTEMS
THERMAX LIMITED
an Indian Company
of D-13, M.I.D.C. Industrial Area, R. D. Aga Road, Chinchwad, Pune 411 019,
Maharashtra, India
THE FOLLOWING SPECIFICATION DESCRIBES THE INVENTION.

This invention relates to refrigerating systems.
In particular, this invention relates to lithium bromide based refrigerating systems.
Lithium Bromide (LiBr) is a chemical similar to common salt (NaCl). LiBr is soluble in water. The LiBr water solution has a property to absorb water due to its chemical affinity. As the concentration of LiBr solution increases, its affinity towards water increases. Also as the temperature of LiBr solution decreases, its affinity to water increases. Further there is a large difference between vapour pressure of LiBr and water. This means that if we heat the LiBr water solution, the water will vapourise but the LiBr will stay in the solution and become concentrated.
Lithium Bromide (LiBr), is used to absorb the vapourised refrigerant after its evaporation at low pressure. This solution, containing the absorbed vapour is heated at a higher pressure. The refrigerant vapourises and the solution is restored to its original concentration for re-use.
When the refrigerant undergoes a series of evaporation, absorption, pressurisation, vapourisation, condensation, throttling, and expansion processes, absorbing heat from a low temperature heat source and releasing it to a high temperature sink, so that its state is restored to its original one, it is said to have completed a refrigerating cycle


In conventional Lithium Bromide - water Absorption chillers refrigerant water is sprayed on the tubes. Inside the tubes water that is to be cooled flows (Process water). Refrigerant water pick ups the heat from process water and cools the process water. Refrigerant water is saturated and is under high vacuum. At high vacuum, temperature of water is very low. Hence refrigerant water is able to pick up heat from process water. Cooled Process water is now used for many application like air-conditioning (cooling of air), reaction cooling, Cooling milk etc.
This indirect type of system is used due to two main reasons.
1- To maintain refrigerant water at lower temperature it should be in vacuum. It is easy to ensure vacuum when system is compact and sealed. If vacuum breaks refrigerant temperature cannot be maintained at lower temperature. In turn it cannot cool process water.
2- Absorption system with water as a refrigerant uses Lithium Bromide as Absorbent. This liquid is very corrosive when in contact with oxygen. Compact and sealed system ensures no ingress of air, which contains oxygen. Thus indirect type of system which cools process water as mentioned above will avoid corrosion problem.
The conventional Li Br vapour absorption system having a simple single effect conventional absorption chiller comprises an evaporator, an absorber, a regenerative heat exchanger, a generator and a condensor
. Using same principle multi effect chillers are manufactured. They are double effect, Triple effect, half effect, Single- double effect etc. The energy

supplied can be in the form of Steam, hot water, Direct firing, Exhaust of Engine and the like.
In the single effect apparatus the evaporator consists of a tube bundle, an outer shell, distribution trays, and a refrigerant pan. The chilled water flows inside the tubes. A refrigerant pump circulates the refrigerant from the refrigerant pan into the distribution trays. From the trays the refrigerant falls on the evaporator tubes. The shell pressure is very low (»6mmHg). At this pressure the refrigerant evaporates at a low temperature (»3.7°C) and extracts latent heat of evaporation from the water being circulated through the evaporator tubes. Thus the water being circulated through the tubes becomes chilled. The boiling point of water is directly proportional to pressure. At atmospheric pressure water boils at 100°C. At lower pressure it boils at lower temperature. At 6mmHg absolute pressure the boiling point of water is 3.7°C.
The absorber consists of a tube bundle, an outer shell (common with the evaporator), distribution trays, and an absorbent collection sump. Concentrated absorbent solution (»63.4%) from the generator is fed into the distribution trays. This solution falls on the absorber tubes. Concentrated absorbent has an affinity to water. Hence the vapourised refrigerant from the evaporator section is absorbed. Due to this absorption the vacuum in the shell is maintained at a low pressure and ensures the correct chilled water temperature. The concentrated absorbent becomes diluted. During this dilution the 'Heat of Dilution' is generated. This heat is removed by the


cooling water being circulated in the absorber tubes. The diluted absorbent (»59%) collects in the bottom of the shell.
In the regenerative heat exchanger, the cool diluted absorbent is pumped to the generator by the absorbent pump. It first passes through the heat exchanger where it absorbs heat from the concentrated absorbent. The solution then enters the generator. The heat exchangers serves to heat up the cool absorbent solution before it enters the high generator for reheating. This reduces the heat input required in the generator. This reduction in the energy input required increases the efficiency of the cycle.
The generator and condensor tube bundles are enclosed in a shell and are separated by an insulation plate. The generator consists of a shell & tube heat exchanger. Heat is supplied to the Generator by means of the Steam. The diluted absorbent surrounds these tubes and is heated. The temperature of the solution increases until it reaches the boiling point. The absorbed refrigerant boils out of the solution. The solution concentration increases (to «63%). The absorbent which has become concentrated in the Generator drains to the absorber to begin a new absorbent cycle. The vaporised refrigerant generated passes through the eliminators and goes to the Condensor.
Refrigerant vapourised from the absorbent passes through the eliminators to the condenser. Here the cooling water enterings from the absorber which flows in the condensor tubes, condenses all these refrigerant vapours. The refrigerant vapour condenses on the outside of the condensor tubes, heating


the cooling water, and collects in the bottom of the condensor. The condensed refrigerant flows to the evaporator.
Limitations of the prior art Indirect Absorption chiller.
1- It is well known that lower the refrigerant temperature lower is capacity of the chiller. Since there need to be temperature penalty for indirect system refrigerant temperature need to be few degree lower than required chilled or process water temperature. If direct absorption chiller is used then refrigerant temperature will be higher(equal to process water temperature) and performance of the chiller will be better both in capacity as well as energy supplied per capacity unit.
2- Water freezes at zero degrees centigrade. If due to some reason water freezes in the tubes, tubes may get punctured. In such a case there will be loss of vacuum and chiller will stop giving chilled water. Also there is danger of corrosion. Hence usually to keep some safety chilled water is not offered below 3.5 Deg c. If temperature is required below 3.5 Deg C brine is used inside the tubes. But brines are costly, corrosive and also cannot be used many places. One such example is food industry.
In accordance with the present invention as described with reference to the accompanying drawing, from the evaporator a pump takes water first at certain height and this water will come down more than 10 meter (say 12 meter) to reach to tank 1 bottom. From Tank 1 through an overflow it will flow to Tank 2. Since water is transferred from Tank 1 to tank 2 only by over flow water level in tank 1 will always be maintained above the opening of inlet pipe to tank 1 . This water level acts as a seal so that no air can


enter in pipe connecting from Evaporator to Tank 1. The height of the pipe is more than 10 meters. Hence water from tank 1 cannot rise above 10 meters in pipe. From tank 2 water is pumped by ordinary water pump to a process which could be air handling unit or heat exchanger or direct contact type process. After doing COOLING WORK this water will return to tank 3. In tank 3 level switch or a simpler arrangement is employed so that if water level falls below certain level pump 3 is switched OFF. This will ensure that in no case level in Tank 3 will be below outlet pipe of tank 3 . Usually Pump l and Pump 2 will be of special type which will be leak proof so that no air can enter from body of the pumps.
When the Chiller is not working or the pump 1 and pump 2 are not working water level in tank and 12 meter height of pipe will maintain the seal in the pipe so that no air ingress is possible.
The system in accordance with this invention can use directly refrigerant water, which can be very near to freezing point of water. Since water is not flowing through small diameter of tubes (of which walls are giving away the heat) there is no danger of ice formation.
Further, since refrigerant temperature can be equal to desired process water temperature, capacity of chiller as well as energy consumption per capacity unit will be better than indirect type (conventional) Absorption chiller.
While considerable emphasis has been placed herein on the particular features of the construction and features of the chiller configured to cool water and the improvisation with regards to it, it will be appreciated that


various modifications can be made, and that many changes can be made in the preferred embodiment without departing from the principles of the invention. These and other modifications in the nature of the invention or the preferred embodiments will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the invention and not as a limitation.