What is the difference between a refrigeration unit and a heat pump unit?

What is the difference between a refrigeration unit and a heat pump unit? Different components, different structures and different functions can be realized.

The refrigeration unit only has a single refrigeration function, and the main components of the system are compressor, condenser, throttling component and evaporator, and the refrigerant flows in the evaporator and condenser in one direction. The heat exchange area of evaporator and condenser of refrigeration unit can be reduced appropriately, and the capacity of compressor can also be reduced appropriately, and the balance can be achieved by increasing the air volume of condenser fan and evaporator fan. There is no need for liquid storage tank in the pipeline of refrigeration unit system, and gas-liquid separator is not a necessary component.

In order to switch the cooling and heating modes of the heat pump unit, besides the compressor, condenser, throttling component and evaporator, there is also a very important component-the four-way reversing valve. The system switches the cooling and heating modes of the heat pump unit by switching the four-way reversing valve. However, when the four-way reversing valve of the heat pump unit is switched, more liquid refrigerant will flow to the compressor in a short time. In order not to cause the liquid impact of the compressor and prevent the liquid refrigerant from directly flowing back to the compressor, it is necessary to add a gas-liquid separator with appropriate size on the compressor suction pipeline. The refrigerant flow required for heating operation of the unit is less than that required for cooling operation. Excess refrigerant needs to be stored in a special storage tank, and a special storage tank is set in the heat pump unit system.

What is the difference between water source heat pump refrigeration unit and ground source heat pump refrigeration unit? What should I pay attention to when designing? In fact, ground source heat pump including water source heat pump is very specific, and the ground source heat pump you mentioned should be ground source heat pump.

Simply put, water source heat pump relies on underground water for heat exchange, and ground source heat pump (soil) relies on soil for heat exchange.

When designing a water source heat pump system, it depends on whether there is a suitable heat source, that is, the groundwater is not fully filled with water.

Understand the local water quality and geological conditions to determine whether the water source heat pump can be used, and determine the number of water intake wells and recharge wells.

Ground source heat pump is suitable for places without groundwater or other heat sources! Buried pipes are expensive and occupy a large area.

What is the difference between air-cooled heat pump unit and air-energy heat pump unit? The main functions used are different. The air cooling module is mainly used for cooling and heating. Air source heat pump heating is mostly used. But there is not much difference in structure, and the principle is similar.

What's the difference between Yantai Ice Wheel Refrigeration Unit and Dalian Sanyo Refrigeration Unit? The refrigeration unit of Yantai Ice Wheel has a relatively large refrigeration capacity and a relatively low price. It is suitable for systems with a relatively large refrigeration capacity, such as more than 500KW, and it is better for ammonia systems. Manual operation is required. If it is used in a Freon system or a highly automated system, it is not very suitable.

Dalian Sanyo's units are suitable for systems with less refrigeration requirements, and can only be used for Freon systems, with good automation. Disadvantages: it can't be used in ammonia system, and the price is higher.

What is the difference between air-cooled heat pump unit and air-source heat pump unit? Air-cooled heat pump is air-source heat pump, which is a name peddled. Air-cooled heat pump, air source heat pump, air source heat pump

What is the difference between a single water cooling unit and a heat pump unit? What's the difference between their working principles? There is a difference in essence. Water cooling relies on water as a thermal conductor to radiate heat into the air. The principle of heat pump is similar to that of refrigerator and air conditioner.

What is the difference between direct air cooling unit and indirect air cooling unit of steam turbine? At present, air cooling of power stations at home and abroad can be divided into two categories: one is indirect air cooling system, and the other is direct air cooling system. Indirect air cooling system is divided into mixed air cooling system and surface air cooling system. The world's first 1500KW direct air-cooled generator set was put into operation in a pit mouth power station in Germany on 1938, and it has been more than 60 years since then. Several typical air-cooled units are: 1958, 2X36MW unit of Yidabad cold power station put into operation, 1968, Spain 160MW unit put into operation, 1978, 365MW unit of Waddock power station in Wyoming, USA put into operation, and Matimba power station in South Africa/kloc-0. At present, the maximum unit capacity of indirect air cooling system of surface condenser is 6X686MW at Kendall Power Station. The maximum unit capacity of indirect air cooling system of hybrid condenser is 300MW, and the 325MW (provided by Harbin Air Conditioning Co., Ltd.) which is currently put into operation in Iran performs well. Among the installed capacity of air-cooled units in the world, the installed capacity of direct air-cooled units accounts for 60%, and that of indirect air-cooled units accounts for about 40%.

1.2 characteristics of direct air cooling system

After decades of practice, both direct air cooling and indirect air cooling power plants have been proved to be feasible. However, it does not rule out the problems caused by various reasons during the implementation of the air cooling system, such as severe cold, intense heat, strong wind, unreasonable system design and improper implementation management.

The implementation practice of 200MW air-cooled units that have been put into operation in China proves that some of these problems have been solved.

Compared with the air cooling system of power station, the direct air cooling system has the following main features:

(1) high back pressure;

(2) Due to the adoption of forced ventilation fan, the power consumption is high;

(3) Forced ventilator is noisy;

(4) Steel platform occupies less land than reinforced concrete tower;

(5) The benefit is about 30% larger than that of indirect cooling system, and the heat dissipation area is about 30% smaller than that of indirect cooling system;

(6) Cost economy.

2. Composition and scope of direct air cooling system

2. 1 thermal system of direct air cooling system

Direct air cooling system, that is, the steam turbine exhaust directly enters the air cooling condenser, and its condensate is discharged into the regenerative system of the steam turbine unit by the condensate pump.

2.2 Composition and scope of direct air cooling system

The equipment and pipelines within the range from the exhaust port of low-pressure cylinder of steam turbine to the inlet of condensate pump mainly include:

(1) exhaust pipe of low-pressure cylinder of steam turbine;

(2) air-cooled condenser tube bundle;

(3) Condensed water system;

(4) air extraction system;

(5) hydrophobic system;

(6) ventilation system;

(7) direct air cooling support structure;

(8) Automatic control system;

(9) Cleaning device.

3. Functions and characteristics of components of direct air cooling system

3. 1 exhaust pipe

For large-capacity air-cooled units, the diameter of exhaust pipe is relatively thick. The 665MW direct air cooling unit of Matimba Power Station in South Africa has two cylinders and four exhaust pipes with a diameter of about 2XDN5000. According to the design of several air-cooled power plants in China, the exhaust pipe diameter of 300MW units is above DN5000, and that of 600MW units is around DN6000.

At present, after the exhaust pipe is led out from the A train of the steam turbine room, there are two ways to arrange the transverse exhaust header, one is the low position arrangement, and the other is the high position arrangement. It is difficult to optimize the wall thickness of large-diameter pipeline, which is also one of the key points that affect the project cost.

3.2 cooling device of air-cooled condenser

(1)A-type architecture:

Double-row tube bundles are generally composed of steel pipes and fins, and the anticorrosion surface is galvanized. Single-row tubes are steel tubes with aluminum fins, which are brazed on large-diameter rectangular elliptical tubes. Its upper end is welded to the steam pipeline and its lower end is connected to the condensate main pipe. Every 8 pieces or 10 pieces form a radiating unit, and the tube bundle of each unit forms an included angle of 59.50-60.50 degrees, forming an A-shaped structure.

(2) Cooling element:

The cooling element is a finned tube, which is the core of the air cooling system, and its efficiency directly affects the cooling effect of the air cooling system. Basic requirements for the efficiency of finned tubes;

A. good heat transfer efficiency; B. good temperature resistance; C. good thermal shock resistance; D. good atmospheric corrosion resistance; E. dirt is easy to clean: f. enough pressure resistance, small pressure drop in the pipe: g. small air side resistance; H. good mechanical vibration resistance; Reduce the manufacturing cost.

The cooling element of air-cooled condenser adopts multi-row tubes with round tubes and fins, such as Foucault cooling element. Later, it was developed into a large-diameter oval pipe sleeve with rectangular fins as double-row pipes. Recently, a large diameter flat tube finned tube, also called single row tube, has been developed. It should be said that these three cooling elements have been successfully applied in direct air cooling system. At present, the main manufacturer of steel multi-row pipes is German BDT company, and its domestic production base is located in Zhangjiakou. The main manufacturer of double-row pipes is GEA (Germany), and the domestic production bases are Jieyi Company in Taiyuan and Harbin Air Conditioning Co., Ltd.; HAMON, a former Belgian company, produces single-row pipes, and there is no production line in China. After being acquired by BDT headquarters last year, it merged with BDT to form the same company. This year, two production lines were put into production in Tianjin. Up to now, all three types of pipes have joint venture production lines in China, or they are independently produced.

(3) Composition of double-row tubes

Oval steel tube steel fin, with diameter of 100X20mm, welded with rectangular fin. The two ends of the tube are semicircular and the middle is rectangular. First of all, the fin spacing of the inner tube on the air receiving side is 4mm, and the fin spacing of the outer tube is 2.5 mm The tube spacing is 50mm, and the number of tubes can be changed according to the heat dissipation area. A plurality of tubes are arranged into tube bundles, and every 8 or 10 tube bundles form a heat dissipation unit, and the two tube bundles form an A-shaped structure of about 60 degrees. Single-row tube structure: oval steel tube steel fins with a diameter of 200×20mm, semicircular at both ends and rectangular in the middle. Serpentine fin, brazed on oval steel pipe.

The lower end of the finned tube is connected with a water collecting tank for collecting condensed water. The water collecting tank is connected with the countercurrent unit. The root of the countercurrent unit tube is provided with an exhaust port.

(3) Layout of heat dissipation units

Each unit is arranged vertically parallel to the direction of the steam turbine room and can be divided into columns and rows. 300MW units are arranged in 6 rows, 4 rows or 5 rows, with a total of 24 or 30 units; 600MW units are arranged in 8 rows, 6 rows, 7 rows or 8 rows, with a total of 48, 56 and 64 cooling units. Ko structure

The heat dissipation unit can be divided into downstream unit and countercurrent unit. Downstream means that steam is from top to bottom and condensate is from top to bottom. When the steam in the downstream unit can not be completely condensed, the remaining steam is condensed in the countercurrent unit, and the flow directions of steam and condensate are opposite, that is, steam flows from bottom to top, and water flows reversely from top to bottom.

As we all know, there is always non-condensable gas moving with the steam in the execution steam of the unit. The counter-flow device is mainly used to remove non-condensable gases and prevent freezing in cold areas.

In cold regions, the area ratio of upstream and downstream units is about 5: 1, and the number of units is about 2.5: 1. Each row of radiator of 600MW unit is composed of 2 sets of countercurrent units, and each row of radiator of 300MW unit is composed of 1 set of countercurrent units. The sum of the heat dissipation areas of upstream and downstream units of each unit is the total heat dissipation area. This area needs a certain margin in summer, because the actual pollution on the tube bundle fins is greater than the experimental value, the instantaneous wind speed in windy areas is higher than 4.0m/s, and the mechanical processing quality of the tube bundle is defective, especially the temperature field changes after the power plant is put into operation, which is more than 2.0℃ higher than the temperature measured by the weather station and 3.0℃ lower in the town. These problems need to be paid attention to.

3.3 air extraction system

The upper end of the countercurrent unit tube bundle is provided with an exhaust port, and the exhaust port is connected with a group of air suction pumps. Suction pump sucks air, which is divided into execution and start. Start inhalation time is short. The system volume of 300MW unit is about 5300m3, and at the same time, the back pressure is reduced, making it close to the implementation back pressure. The time is about 40 minutes.

Pay attention to the partial pressure of steam and non-condensable gas when pumping, and do not pump out steam when pumping. The pumping system also ensures the back pressure of the system.

3.4 Condensed water system

In the water collecting tank at the lower end of the cooling unit, the condensed water collected from the finned tube bundle flows into the hot well on the platform ground or below the ground, and then is sent to the condensed water tank, which is sent back to the thermal system by the condensed water pump.

3.5 Ventilation system

At present, the direct air cooling system adopts forced ventilation, and the large-diameter axial flow fan is suitable for large air cooling units. Air can be regulated by single speed, double speed and frequency conversion. According to the engineering conditions, any one or several optimal combination schemes can be selected. Based on the design and implementation experience at home and abroad, in cold areas or areas where the temperature difference between day and night changes greatly, frequency conversion speed regulation is adopted, which makes the fan beneficial to the implementation of variable working conditions and reduces the auxiliary power consumption. In order to reduce the number of fans, large-diameter axial fans with diameters of 9. 14m and10.36m are usually used. ; The gearbox is easy to leak oil and wear, so it is safer to use imported equipment at present. There is a joint venture company in China to do frequency conversion governor, which greatly reduces the cost compared with imported equipment. In order to reduce noise, the selection of fan blades is very important. The blade is made of FRP, which is durable and should not be damaged. In recent years, China has increasingly strict requirements for noise generated by direct air-cooled power stations. According to the requirements of Class III standard of Environmental Protection Standard Industrial Zone, the sound pressure level of fan noise at a distance of 150m from the air-cooled condenser platform shall not exceed 65dB(A) during the day and 55dB(A) at night. The choice of fans is generally low-noise or ultra-low-noise fans. At present, the production level of this kind of fans in China is difficult to meet the requirements of noise standards. Usually, the imported axial flow fans produced by Italy's COFIMCO company and Poland's HOWDEN company are sensitive to the changes of environment, unit load and other factors in the direct air cooling system, and the frequency of changes is also relatively frequent. In order to achieve the above three tasks, the automatic control system must control the air flow and steam flow. For the radiator unit, it is necessary to assemble a cleaning pump to remove the dirt on the finned tube, such as sundries and dust accumulation caused by strong winds at ordinary times. Cleaning has high-pressure air or high-pressure water, and the latter is better than the former. The pressure of the high-pressure water pump is 130ram (atmospheric pressure) and 10 ton per hour. Generally speaking, the annual cleaning support structure is the main load-bearing device of direct air cooling device. The upper part is a steel truss structure, and the lower part is a reinforced concrete column and foundation. Under various loads, the structural system is huge and complex. Foreign countries already have mature design and manufacturing experience. Compared with the international advanced level, the research on the supporting structure of large direct air-cooled units in China is relatively late at present, and the design and mechanical calculation of the supporting structure need to be developed. At present, the supporting structural steel trusses of several air-cooled power stations under construction in China are all designed by foreign companies.

4. Several problems to be studied in direct air cooling system.

The direct air cooling system is still in its infancy in China, and it lacks experience in design and implementation. Power plant owners not only care about the economy of air cooling system design optimization, but also care about the safety of air cooling system. The so-called safety mainly includes two aspects: one is whether high temperature in summer can ensure the full development of design assessment points, and the other is whether it can effectively prevent freezing at low temperature in winter. Therefore, in the design and implementation of direct air cooling system, it is necessary to study and summarize the following topics:

4. 1 gale influence

The direct air cooling system is sensitive to different wind directions and different wind speeds, especially when the wind speed exceeds 3.0m/s, it will have a certain impact on the heat dissipation effect of the air cooling system, especially when the wind speed exceeds 6.0/s, different wind directions will cause heat reflux to the air cooling system and even reduce the fan efficiency. In order to minimize the influence of strong wind, it is necessary to study the high temperature period in summer in the design. In the design and layout, the wind direction with the highest frequency at a certain wind speed should be avoided, and even the distance from train A should be appropriately widened. In the process of implementation, relevant data are collected through meteorological observation and summarized according to the change of power generation load of power plant. Before the implementation of the project, the necessary physical model or numerical simulation test is carried out to guide the design, and the collected data will be compared and summarized in the future.

4.2 Hot air backflow

When the power plant is running, the cold air rises through the hot air discharged by the radiator, showing a plume state. When the strong wind blows from the back of the furnace to the platform radiator, and the wind speed exceeds 8m/s, the plume is destroyed and the hot air flows back. The updraft of hot air is dropped below the steel platform by the wind pressure behind the furnace, and such hot air is sucked by the fan and then returned to the circulation in the form of hot air. Even the fans in the outermost row rotate in the opposite direction. In the project, an air wall is added to overcome the hot air backflow, and the height of the air wall should be determined by the design.

4.3 Platform height

The platform height of the supporting structure is comprehensively considered in combination with the overall planning of the power plant and the requirements of the air cooling system itself. The principle of determining the height of the platform is to make the lower part of the platform have enough space so that the air can flow to the fan smoothly. The higher the platform, the better the air intake, but it will increase the engineering cost. At present, there is no perfect theoretical formula for how to reasonably determine the platform height, and everyone only has habitual experience to calculate it. The solution to this problem is based on years of experience, through model calculation under different conditions and testing in the process of field implementation, to study and summarize an ideal calculation method.

4.4 antifreeze protection

Anti-freezing of direct air cooling system is an important problem affecting the safe operation of power plant. From the experience of foreign design and implementation, there are many measures to ensure that anti-freezing is effective.

A. the design adopts a reasonable area ratio of upstream and downstream, that is, K/D structure. The "K/D" in severe cold areas takes a small value, and the "K/D" takes a large value in hot areas.

B. add a wind wall to prevent strong winds.

C, adopting a reversible fan to form an internal hot air circulation.

D correctly calculate the relationship between the exhaust pressure of the steam turbine and the ambient temperature, so as to determine the reasonable execution mode of the fan.

E. stop the fan of the swimming unit first, and then stop the fan of the countercurrent unit.

F. strictly control the supercooling degree of condensed water.

G. strictly control the outlet temperature of the countercurrent tube bundle and adjust the operating hours of the countercurrent fan in time. The above are some measures for anti-freezing protection in design and implementation. How to apply them reasonably and properly still needs to be studied and summarized according to different engineering conditions in design and field.

5. Operating conditions of air-cooled steam turbine

5. 1 operating conditions of air-cooled turbine

A.TRL condition-capacity condition

B.T—MCR condition-maximum continuity condition

C.VWO state-fully open valve state

D.THA working conditions-rated working conditions

E. block back pressure.

5.2 Matching relationship of air-cooled units

(1) The boiler capacity should match the steam intake of the steam turbine under VWO conditions;

(2) The maximum continuous power of the generator is matched with the unit;

(3) The matching relationship of air cooling device shall meet the following conditions at the same time:

A. The capacity of air cooling device shall ensure the rated power under T-MCR working condition at the specified temperature in summer, and a certain air cooling unit or equivalent air volume margin shall be reserved;

B. Under the condition of typical annual maximum temperature, there is a margin of more than 15kpa between the inlet steam back pressure value of the air cooling device and the safe limit back pressure of the unit under VWO working condition, so as to adapt to the safe implementation under adverse environmental wind speed changes;

C. When the fan of the air-cooled unit is shut down or overhauled, the normal back pressure of the unit is within the limit back pressure range.

6. Conclusion

The design of direct air cooling system for large generator sets is applied late in China and even later in Inner Mongolia. At present, air-cooled power plants such as Shangdu Power Plant, Fengzhen Phase III, Tuodian Phase III and Wulashan are only in the stage of detailed construction design or bidding, lacking design and implementation experience.

Is there any difference and connection between water chillers and heat pumps in central air conditioning? Is it true that chillers can only cool, and heat pumps can also cool? Yes, your understanding is correct. The water chiller can only produce cold water, while the heat pump can produce cold water and hot water (of course, not at the same time, there is a four-way reversing valve inside the unit to switch the flow direction of refrigerant for control, that is, to control the condenser and evaporator during refrigeration to be converted into the evaporator and condenser during heating:). Cold water can be used in summer and hot water can be used in winter.

What is the difference between a heat pump and a refrigerator? The principle is the same.

The refrigerator is used for refrigeration, and excess heat is discharged;

The heat pump is used for heating, and the excess cold energy is discharged.

Can the water source heat pump unit be heated by the cooling water of the refrigeration unit in summer? Yes, add a heat exchanger to the cooling system.