Why is absorption refrigeration not commonly used?

Absorption chillers.

It is a form of evaporative refrigeration. Absorption refrigeration is achieved in a timely manner by consuming heat energy. It is a type of refrigerator that is powered by thermal energy. It's similar to how we feel cold when we hold an ice cube in our hands.

1. Properties of lithium bromide aqueous solution.

Absorption refrigeration concentrations are usually binary solutions consisting of two solutions with different boiling points, where the low-boiling component is the refrigerant.

The high boiling point group is divided into absorbents, refrigerants and absorbents are collectively referred to as working fluid pairs.

It has a large latent heat of evaporation, is not combustible, non-combustible, non-toxic or less toxic, and is non-corrosive and cheap to equipment.

Requirements for absorbent: under the same pressure, the boiling point of the absorbent is higher than that of the refrigerant, and the higher the boiling point difference, the better, so that the generator can produce high-purity refrigerant vapor, which can improve the thermal coefficient of the refrigerator. It has a strong absorption capacity, which can reduce the circulation amount of the absorbent, reduce the heat required by the generator, the heat released from the absorption and the power consumption of the pump.

It has a large thermal conductivity.

Smaller density and viscosity, smaller specific heat capacity.

And good chemical stability, non-toxic, non-combustible, non-corrosive to metal, cheap, in addition to absorbents and refrigerants must be non-azeotropic solutions.

At present, there are many available working fluids, and only NH3-H2O and Libr-H2O are widely used, the former is used for cryogenic systems below 0 degrees Celsius, and is less used in China, and the latter is widely used in air conditioning systems.

Because the absorption is refrigerated with. Refrigerant refrigeration is very high compared to sucking finger cold and cold. The power on board is very small, and the secondary use is now this. refrigerant refrigeration, this way. There can be 1000 watts of power expenditure of 3000 watts, so it is very time-sensitive.

Absorption refrigerators are not refrigerated – the lines are displaced.

Solution: In the process of transportation and handling, the packaging of the absorption refrigerator should be stable and firm, the placement should be smooth, and the handling should be careful, if the indoor ground is slightly uneven, the refrigeration effect will be poor. The foot of the domestic absorption refrigerator is equipped with adjustable screws, and the top surface of the refrigerator is leveled through the adjustment of the screws until the refrigerator works normally.

Absorption refrigerators do not refrigerate - ammonia leaks.

Exclusion method: first check the weld of each connecting pipe, check the method, the user can use the litmus test paper used in the laboratory to attach to the suspicious weld joint, if the test paper turns blue, it means that the weld has ammonia gas running out, and then repair the welding, if the hole is not big, you can stop the refrigerator heating and work, and the user will repair the hole with solder; If the hole is large, it should be repaired by the refrigerator maintenance department.

Absorption refrigerators do not refrigerate – poor refrigeration or no refrigeration.

Troubleshooting: Check the cause of the heat source interruption and resume heating so that the refrigerator continues to work.

Inspect the blockages in the equipment and pipelines, and carry out maintenance and troubleshooting.

According to the requirements on the refrigerator instruction manual, the displaced tube is corrected.

After checking the leakage part in the refrigeration system, weld and repair, and then add an appropriate amount of ammonia according to the ammonia concentration requirements of the instruction manual of the absorption refrigerator.

Because absorption refrigeration, the refrigeration efficiency and the way it is refrigerated are not the smartest and the most advanced.

Therefore, it will gradually be phased out, and absorption refrigeration will become less commonly used.

The main reason why Western absorption refrigeration does not need to be used is that there are many new products now, and they have been able to completely replace these, so there is no need to use the old one.

How absorption refrigeration is not commonly used. If absorption refrigeration is not commonly used, it should be varied, and it is mainly based on the variety of this one.

There must be a lot of reasons why this is diluted to the point where it is not commonly used, and there must be a lot of reasons why it is not commonly used5

Now it is absorption refrigeration and is not used very often.

(1) Use a working heat source (such as water vapor, hot water and gas, etc.) to heat the solution with a certain concentration delivered by the solution pump from the absorber in the generator, and evaporate most of the low boiling refrigerant in the solution.

2) The refrigerant vapor enters the condenser, and is condensed into a refrigerant liquid by the cooling medium, and then depressurized to the evaporation pressure through the flow restrictor.

3) The refrigerant enters the evaporator through throttling, absorbs the heat in the cooling system and intensifies into refrigerant vapor under evaporation pressure.

Structure:

The absorption refrigeration device is composed of a generator, a condenser, an evaporator, an absorber, a circulating pump, a throttle valve and other components, and the working medium includes a refrigerant for producing cold capacity and an absorbent for absorbing and desorbing the refrigerant, and the two constitute a working fluid pair.

An absorption chiller is very different from a reciprocating or centrifugal chiller in that it does not have a moving prime mover. There are two types of absorption refrigerators, namely ammonia-water absorption type and lithium bromide-water absorption type.

They all answered correctly, and I conclude that the main difference between absorption and adsorption is the difference between the medium pairs. Absorption is the adsorption of a gas and a liquid as a pair of working fluids, while adsorption is the adsorption that occurs between a solid and a gas or between a solid and a liquid.

I can only tell you about absorption refrigeration. Absorption refrigerator refers to a refrigeration device that uses the characteristics of the solution to complete the working cycle and produce cold capacity. Absorption refrigeration is also a kind of evaporative refrigeration, which relies on refrigerants to absorb heat by low-pressure evaporation in the evaporator.

Unlike compression refrigeration, absorbers and generators are used instead of compressors. There are lithium bromide-water absorption refrigeration devices, ammonia absorption refrigeration devices and so on. No explanation was found for the adsorption formula.

See "Refrigeration Technology Q&A", edited by Shanghai Fisheries University.

Adsorption refrigeration generally refers to solid adsorption refrigeration, the principle is that some solids can adsorb certain gases or water vapor at a certain temperature and pressure, and release them at another temperature and pressure, and this adsorption and release process causes pressure changes, which is equivalent to the role of a refrigeration compressor. Adsorbents include silica gel, activated alumina, zeolite molecular sieve, activated carbon, etc.

Absorption refrigeration is a refrigeration method that composes a two-element solution with two substances with different boiling points, with a low boiling point as the refrigerant and a high boiling point as the absorbent, and completes the working cycle to obtain cold capacity. The working fluid pairs are generally water and lithium bromide, ammonia and water, etc.

The principle of air conditioning and refrigeration.

The compressor compresses the gaseous freon into liquid freon at high temperature and high pressure, and then sends it to the condenser (outdoor unit) to dissipate heat and becomes liquid freon at room temperature and high pressure, so the outdoor unit blows hot air.

The liquid freon enters the evaporator (indoor unit) through the capillary, the space suddenly increases, the pressure decreases, the liquid freon will vaporize, and become the gaseous low-temperature freon, thereby absorbing a large amount of heat, the evaporator will become cold, and the fan of the indoor unit will blow the indoor air through the evaporator, so the indoor unit blows out of the cold air;When the water vapor in the air meets the cold evaporator, it will condense into water droplets and flow out down the water pipe, which is why the air conditioner will produce water.

Then the gaseous freon returns to the compressor to continue compressing and continuing the cycle. There is a component called the four-way valve during heating, so that the flow direction of Freon in the condenser and evaporator is opposite to that of refrigeration, so when heating, cold air is blown outdoors and hot air is blown in the indoor unit. In fact, it is the principle of expelling heat during liquefaction (changing from a gas to a liquid state) and absorbing heat during vaporization (from a liquid to a gas) that I learned in junior high school physics.

Vapor compression refrigeration units can be miniaturized, such as the refrigerator refrigeration system and household air conditioning refrigeration system used now, etc., while the absorption refrigeration unit cannot do it, and it cannot be so small.

The working effect of vapor compression refrigeration is fast, and the refrigeration efficiency is relatively high; However, the working effect of absorption refrigeration is very slow and the working effect is low.

Absorption refrigeration is applied to large refrigeration units, and the investment cost of using this refrigeration unit is very high.

Absorption refrigeration uses naturally occurring water or ammonia as refrigerants, which are harmless to the environment and the atmospheric ozone layer; In addition to the heat energy generated by boiler steam and fuel, low-grade heat energy such as waste heat, waste heat, and solar energy can also be used to achieve the dual purpose of cooling and heating (heating) in the same unit. In addition to the pump and valves, most of the whole set of equipment is heat exchanger, which operates quietly and has low vibration; At the same time, the refrigerator operates in a vacuum state, with simple structure, safe and reliable, and easy installation. In the current situation of energy shortage, power shortage, and increasingly severe environmental problems, absorption refrigeration technology has received extensive attention with its unique advantages.

1) There is no motive force, and the thermal principle is directly used, so the machine is sturdy and vibration-free, less noisy, and can be installed in any place, from the basement to the roof.

2) Water is used as a refrigerant, which is easy to obtain and has high safety.

3) It can directly use the heat source, it can use low-pressure steam, hot water, and even waste steam and waste heat, and the power consumption is less, which is only equivalent to 2%-9% of the centrifuge with the same capacity.

4) It is easy to change the load and has a wide range of adjustment (the refrigeration capacity can be adjusted in the range of 10%-100%).

5) Simple structure and easy operation.

The disadvantage is that the lithium bromide aqueous solution is very corrosive to metals in the atmosphere, so the requirements for equipment pipelines are high, and the cooling load is large.

1) Pros.

1. The absorption system is most suitable for the year-round air conditioning areas that need air conditioning in summer and heating in winter. At present, the first air conditioning system in the United States and Japan, the absorption system accounts for about more than 80%.

2. Quiet operation, can reduce wear to the minimum (except for the operation of liquid pumps), less failure, simple maintenance.

3. Do not rely on electricity.

4. The capacity control is easy, only the heat source of the generator needs to be controlled.

5. The system has high security, no **.

6. The effect of full load and light load of the system is the same, when the load changes, only need to adjust the heat source of the generator and the amount of water circulation.

7. When the evaporation temperature and pressure are reduced, the absorption capacity is only reduced to a limited extent, and the operation is stable.

2) Cons:

1. When water is used as the refrigerant, low temperature cannot be obtained (the freezing point of water is 0).

2. Improper operation, lithium bromide is easy to crystallize.

Many of today's refrigeration processes use ammonia coolers instead of bromine coolers.

The ammonia cooler occupies a small area, but the storage and heat exchanger of liquid ammonia still have to occupy a point position, but the key is that the COP (energy efficiency ratio) of the ammonia cooler is high, and it can easily reach about it, that is to say, for every 1kw of power input, the refrigeration power can be 4 5kw.

Bromine cooler is, the volume is not small, common direct combustion and absorption two types, direct combustion type can use oil, gas fuel, absorption type of steam absorption, flue gas absorption type and hot water absorption type, but in general, the COP of the bromine cooler is very poor, can go up to 2 is almost against the sky.

Because a single ammonia cooler has a liquid ammonia storage and exchanger, it occupies about the same area as a bromine cooler, but the area of multiple ammonia coolers is definitely smaller than that of multiple bromine coolers.

The current absorption refrigerator, generally in the case of waste heat generation such as flue gas, exhaust steam, and hot water in the factory, in order to avoid waste of waste heat utilization, at this time the use of absorption refrigerator is a good choice, although its COP is not high, but it is better than those waste heat is wasted. For absorption chillers, the minimum temperature requirement for the input heat source seems to be 85 degrees.

The cost of investment is not clear, and I have not been touched. In terms of cost, the ammonia cooler definitely wins, but the absorption bromine cooler uses wasted waste heat, which is more attractive.

After long-term research, the only widely used working fluid pairs are ammonia-water and lithium bromide-aqueous solutions, the former is used in cryogenic systems, and the latter is used in air conditioning systems. Specifically, it is as follows: working fluid pairs with water as refrigerant

Water – lithium bromide, water – lithium chloride, water – lithium iodide, water – calcium chloride. Ammonia as the refrigerant working fluid pairs: ammonia - water, ethylamine - water, methylamine - water and sodium thiocyanate - ammonia, etc.

Alcohol as the refrigerant working fluid pair: methanol is usually used as the refrigerant, mainly methanol-lithium bromide, methanol-zinc bromide, and methanol-lithium bromide-zinc bromide ternary solution working fluid pair. Freon as the refrigerant working fluid to:

Among them, the working fluid pairs composed of R21, R22 and tetraethanol dimethyl ether and other organic substances are mainly used.