انواع مبدلهای حرارتی
Before dealing with the types of heat exchanger, it is necessary to have an explanation about the heat exchanger. In the HVAC industry, one of the most important components in all systems is the heat exchanger. A heat exchanger is a device in which two or more fluids transfer heat together. The purpose of this heat transfer is to cool or heat a fluid or an environment. Usually, the design of this equipment is such that the fluids flowing in it do not mix together.
Heat exchangers are usually classified based on factors such as design structure, fluid flow arrangement, refrigerant type and working pressure, contact surface, etc., which is the most common classification based on design structure. In this article, the types of heat exchangers are reviewed based on the design structure and fluid flow arrangement.
انواع مبدل حرارتی براساس آرایش جریان
parallel flow heat exchanger
In these converters, the direction of cold and hot flow are parallel and in line with each other, in such a way that the cold and hot flow enters from one side of the converter and leaves from the other side. At the beginning of the path, two fluids have the largest temperature difference with each other, and at the end, the difference reaches the lowest level. Heat transfer has a direct relationship with the temperature difference, and the greater the temperature difference between two fluids, the more heat transfer takes place. As a result, in the parallel flow at the inlet of the converter, there is the highest heat transfer and it gradually decreases. In parallel flow converters, at no point in the path does the temperature of the cooling fluid heat up more than the temperature of the fluid.
Countercurrent Flow Heat Exchangers
In these converters, the flow direction of two fluids is parallel to each other but opposite to each other. In this way, the cold fluid (coolant) enters from one side of the converter and the hot fluid enters from the other side, and along the way, these two flows are parallel to each other.
In these exchangers, the temperature difference of the two fluids is almost equal at every section, so the amount of heat transfer is the same and uniform at all sections.
Heat exchangers with perpendicular flow (Cross Flow)
In these converters, the directions of cold and hot flows are perpendicular to each other. One of the most well-known converters with this design is car radiator and heating radiator. In these converters, which are also known as cross-flow converters, there are two concepts called mixed flow and non-mixed flow. Mixing and non-mixing depends on the velocity components. If the fluid flow has components in two directions, this flow is called mixed, and the fluid that flows only in one direction is called non-mixed flow. In heat exchangers with perpendicular flow, the flow inside the coils is unmixed. If the coils have fins, the fluid flow outside is also unmixed, otherwise it is considered mixed flow.
انواع مبدل حرارتی براساس ساختار طراحی
In this part, 4 common models of heat exchangers are reviewed based on the design structure.
Tubular Heat Exchanger (Tubular Pipe)
In tubular heat exchangers, there are two tubes of different sizes, one with a smaller diameter and the other with a larger diameter. The smaller tube is placed inside the larger tube and concentric with it. The way these converters work is that one of the fluids flows inside the smaller tube and the other flows in the middle space of the two tubes, and the two fluids exchange heat with each other. In these converters, which are also known as double pipe converters, the inner tube wall forms the heat transfer surface, which is usually finned to increase the surface area of the inner tube.
Design of tubular heat exchanger
In these converters, the two-fluid flow can be parallel (Parallel Flow) or opposite (Counter Flow). Of course, the highest efficiency is related to the opposite flow. In the opposite flow, two fluid inlets are placed in two different directions.
Application of tubular heat exchangers
Tubular exchangers have a simple design and low manufacturing cost and are used for heat transfer in high-pressure fluids. But compared to other competitors, they do not have high heat transfer capacity and efficiency. However, in order to achieve more heat transfer capacity, several of these converters can be placed in a row together, of course, in a vertical direction. The way of heat transfer in this model is that it either changes the temperature of a small volume of fluid by a large amount or changes the temperature of a large volume of fluid by a small amount. Tubular heat exchangers are usually used in the food and air conditioning industries.
Shell and tube heat exchangers
One of the most common types of heat exchangers is the Shell and Tube exchanger. In this converter, which is made of a large cylindrical shell and a number of tubes that are placed inside the shell. One of the fluids enters these tubes and the other fluid enters the converter shell. In this way, the heat transfer process is carried out from the surface of the pipes.
The fluids used in this converter can be both liquid and gas. If only liquid fluid or gaseous fluid is flowing inside the converter, this model is called single phase. In other cases, the converter is two-phase, for example, the fluid inside the coil enters as a liquid and evaporates and turns into a gas with heat transfer. Usually, the coils are made of copper, but in some cases, depending on the type of use, aluminum, steel, brass, etc. can be used.
Shell and tube heat exchanger design
The internal structure and the way of connections and arrangement of coils inside shell and tube converters are very diverse. In these converters, tubes are used either straight or bent in a U shape. In U-shaped coils, this method reduces the resistance of the pipes in the bent area due to bending, and there is a possibility of failure. For this reason, this model is usually used in low capacities. In shell and tube exchangers, there are other components such as tube sheet, baffle, plenum, which are discussed in the article on shell and tube heat exchanger. In these converters, like the tubular converter, the opposite flow has the highest efficiency.
Application of shell and tube heat exchangers
One of the important applications of Shell and Tube converters is the evaporator of air-cooled chillers and the evaporator and condenser of water-cooled chillers. Shell and tube heat exchanger is one of the best choices in applications that are supposed to be performed on a large volume of heat transfer fluid. For this reason, one of the most used converters in industries such as petrochemicals, steel, papermaking, drug production, power plants, etc. is these converters.
Plate heat exchanger
In plate converters, instead of using several tubes, there are a number of plates that are placed in a row and with a small distance from each other. The design and construction of plate heat exchangers is such that two fluids pass through the plates and do not mix. In simpler words, two fluids are flowing between the plates as one in between. The pages are also sealed in the middle.
The surface of these plates are smooth or wavy, and they are usually made of stainless steel to resist corrosion and withstand high temperatures. As the fluid moves between the plates, they have more surface area for heat transfer, resulting in more heat transfer. For this reason, to create a certain amount of heat transfer, plate exchangers have a smaller size than other exchangers.
Since the distance between both plates is small, the fluid will have a turbulent and eddy flow. This feature increases the heat transfer coefficient of the flow and increases the efficiency of the device. On the other hand, due to the large shear stress in the corners of the plates, the amount of sediment in these converters is much less. These positive features of the screen converter have made screen converters widely used in various industries today. Of course, this model can withstand lower pressures than shell and tube exchangers.
Plate converters are divided into 3 categories based on their structure, which are:
A) Gasket Plate Heat Exchanger
In these converters, plastic gaskets are placed between the plates so that it sticks around the edge of the plate and there is no possibility of leakage and mixing of fluids. In these gasketed exchangers, if we intend to change the heat transfer capacity, the number of metal plates can be increased or decreased. This model of converters is suitable for fluids with large volume and low or medium pressure.
b) Brazed plate heat exchangers
In this type, the corrugated plates are connected to each other with the help of a filler material and a soldering process. Brazed plate heat exchanger is used for heat transfer in high pressure fluids.
c) Welded plate heat exchangers
In this model, different plates are placed next to each other and welded together. The cooling and heating capacity of these converters is fixed and it is no longer possible to add or subtract plates. The welded plate heat exchanger has the ability to transfer heat at high temperature and pressure, and thus it is widely used in large industries.
Air cooled or fan converters
In these exchangers, where heat exchange takes place between air and another fluid, there are a number of coils and one or more fans. Hotter fluid flows inside the coils and air is circulated around the coils by a fan. In order to increase the contact surface of the air with the coils and thus increase the amount of heat transfer, the coils are usually equipped with fins. Air particles hit the heated surface of the coil and vane, take the heat from the fluid and cause the fluid to cool. Air-cooled exchangers are divided into three categories: vertical, horizontal and V-shaped.
Application of various types of heat exchangers
As mentioned at the beginning of the text, a heat exchanger is a device for exchanging heat between two or more fluids with different temperatures. This heat exchange is sometimes for heating and sometimes for cooling; Sometimes it is for industrial use and sometimes for air conditioning.
Among the industrial applications of heat exchangers, we can mention food industries, chemical industries, manufacturing industries, power plants, oil and gas refineries, pharmaceuticals, paper industries, etc.
چیلر تراکمی
Compression chiller is one of the types of air conditioning equipment used for cooling and producing cold in buildings and industries. Vapor Compression Chiller operation is based on the compression refrigeration cycle; In this way, in a refrigeration cycle, with refrigerant circulation, heat is absorbed from water and cool water is produced. In construction purposes, this cooled water goes inside the building and exchanges heat with the air inside the building through fan coils or air conditioners and reduces the ambient air temperature. In industrial uses, water from the chiller is used to cool fluids or absorb heat from industrial devices and tools.
طرز کار چیلر تراکمی
The compression chiller consists of 5 main components, including compressor, condenser, expansion valve, evaporator and electricity meter, and these equipments work with each other based on the condensation-steam refrigeration cycle. After absorbing heat from the water in the evaporator, the refrigerant evaporates and enters the compressor as hot steam.
In the compressor, during an isentropic process and by receiving electrical energy, the refrigerant fluid is condensed and its pressure and temperature increase drastically. At the end of the condensation process, the high-pressure hot fluid enters the condenser.
In the condenser, in a constant pressure process, the incoming hot steam exchanges heat with another fluid and the refrigerant vapor condenses (turns into a liquid) and due to the temperature difference, the heat exchange continues until the temperature of the liquid refrigerant continues to decrease. .
After the condenser, the refrigerant liquid passes through the expansion valve and faces a significant pressure drop. Due to the high pressure drop, some of the refrigerant evaporates and absorbs its latent heat of evaporation from the remaining liquid, as a result, the temperature of the refrigerant decreases again.
In this way, the refrigerant flow enters the evaporator as a two-phase fluid (steam and liquid) and evaporates completely by absorbing heat from the water. In the evaporator, the saturated steam also increases its temperature by absorbing heat and turns into hot steam.
Finally, the cooled water in the evaporator circulates for cooling in the fan coils and air conditioners, and the evaporated refrigerant also goes into the compressor to go through the refrigeration cycle again.
کاربرد چیلر تراکمی
The compression chiller is one of the most popular air conditioning equipment that is widely used in industrial applications and also in air conditioning.
Application of compression chiller in air conditioning
One of the most widely used cooling equipment in residential and commercial buildings is compression chillers. The cooling process by these chillers is such that the cold water produced in the chiller is transferred to the fan coil, air conditioner and air cooler. In each of these three devices, the cold water absorbs the heat of the air inside the building and cools the air. At the end, the heated water returns to the chiller. In residential houses, mini chillers are often used due to the low required capacity. Mini chiller is the compression chiller in limited capacities (usually less than 10 tons of refrigeration).
Application of compression chiller in industrial refrigeration
In industries, one of the most important and necessary processes is the cooling of equipment, industrial molds and machinery. In industries, equipment and machines are all sensitive to temperature, and if their temperature increases during operation, it is necessary to control the temperature. Temperature control and cooling are usually done with chillers or cooling towers. Compression chillers are used in industries such as petrochemical, steel, cement, food production, process cooling in pharmaceuticals, plastic injection, etc. In the following video, we have discussed the difference between an industrial compression chiller and an air conditioner.
انواع چیلر تراکمی
Compression chillers are usually classified based on two factors: compressor type, condenser type, and number of units, which is more common to classify based on compressor and condenser type.
Types of compression chillers based on the type of compressor
The compressor is a device that is located after the evaporator and is responsible for increasing the pressure and temperature of the refrigerant. Usually, based on the type of project, the required refrigeration capacity, climatic conditions, etc., the type of compressor is determined. The compressor is one of the most basic and of course the most expensive equipment of a chiller. Therefore, choosing the right type is very important. The types of compressors used in compression chillers are:
Rotary compressor
Rotary compressors consist of an eccentric cylinder and a compression shell. These compressors are often used in very low capacities from 1 to 3 kW and especially mini chillers.
Scroll compressor
Scroll compressors are also used in compression chillers with low capacity (from 5 to about 125 kW) and usually in air conditioning. In this compressor, there are two rotating spirals to condense gas refrigerant, one of these spirals is rotating and the other is fixed. One of the advantages of this compressor is having few moving parts, low vibration, long service life, high efficiency and uniform refrigerant flow. Scroll compressors are usually not repairable.
Piston or reciprocating compressor
Reciprocating piston compressors are used in medium capacities up to 800 kilowatts, and in addition to air conditioning, they are also used in industrial refrigeration. Piston compressors consist of cylinders and pistons, crankshafts, connecting rods, etc., and refrigerant is compressed and discharged inside the cylinder by the reciprocating movement of the piston. In general, the moving parts of this compressor are many, but it is not particularly complicated, which makes its maintenance and repair easy.
Screw or spiral compressor
Screw compressors are used in high capacities (80 to 600 kW), which are used in industrial and air conditioning applications. Two rotary screw compressors are installed in this compressor, and the refrigerant vapor moves and condenses in the space between the two screws. The number of moving parts of screw compressors is small. The distinguishing features of these compressors include low noise, high durability, and continuous capacity control. The performance efficiency of this compressor is higher than the piston model.
Centrifugal or centrifugal compressor
Centrifugal compressors are usually used for large air conditioning and industrial refrigeration projects and in very high capacities. Condensation of refrigerant vapor in these compressors is done by rotating at high speed and centrifugal force. With the help of rotating vanes in the compressor, the flow of refrigerant accelerates and is thrown towards the diffuser. In the diffuser, the speed of the fluid decreases due to the enlargement of the passageway and its pressure increases.
Types of compression chillers based on the type of condenser
One of the main chiller equipment is the condenser, which is located after the compressor and is responsible for removing heat from the refrigerant. Condensing chillers are divided into two categories based on the type of condenser.
Cooled water compression chiller
The condenser in the water-cooled compression chiller is a shell and tube heat exchanger. The refrigerant coming out of the compressor enters the converter shell and water flows as a cooling fluid inside the condenser coils. After absorbing heat from the refrigerant, the water is heated and leaves the condenser and is transported to the cooling tower by the pump. Then the cooled water from the cooling tower goes to the condenser again and flows into the condenser tubes. After leaving the compressor, the refrigerant flows into the converter shell and exchanges heat with the water in the pipes.
Air cooled compression chiller
The condenser in the water-cooled compression chiller is a shell and tube heat exchanger. The refrigerant coming out of the compressor enters the converter shell and water flows as a cooling fluid inside the condenser coils. After absorbing heat from the refrigerant, the water is heated and leaves the condenser and is transported to the cooling tower by the pump. Then the cooled water from the cooling tower goes to the condenser again and flows into the condenser tubes. After leaving the compressor, the refrigerant flows into the converter shell and exchanges heat with the water in the pipes.
The difference between an air-cooled compression chiller and a water-cooled chiller
The efficiency of the air-cooled chiller is lower than that of the water-cooled chiller. Therefore, to provide a specific cooling load, the condenser of the air-cooled chiller needs to be larger than the condenser of the water-cooled chiller. For this reason, the initial cost of the air compression chiller is higher than that of the water chiller.
But it should be noted that we need to use a cooling tower in addition to the water chiller. Therefore, the cost of providing the cooling tower, pump and piping system from the condenser to the tower is one of the side costs of the water chiller. In addition, water chiller maintenance is expensive due to annual acid washing due to water hardness, under drains inside the tower, adding chemicals to water and providing compensatory water.
Air-cooled chiller should be installed on the roof or in the area, but the water-cooled chiller is installed in the engine room and its cooling tower in the roof space; Therefore, it occupies both spaces, i.e. the roof and the engine room.
اجزای اصلی چیلر تراکمی
All compression chillers consist of 4 main components, which are compressor, condenser, expansion valve and evaporator. In this article, the types of condensers and compressors of compression chillers were reviewed, then other components and their types are introduced.
Expansion valve in compression chillers
The expansion valve in compression chillers is responsible for controlling the temperature and pressure of the refrigerant entering the evaporator. The mechanism of the expansion valve is such that by reducing the cross-sectional area of the refrigerant flow path (limiting the flow path), it causes a severe pressure drop in the refrigerant, which ultimately leads to a decrease in the temperature of the refrigerant. The reason for the decrease in refrigerant temperature is the evaporation of part of the refrigerant due to high pressure drop; In fact, the latent heat of evaporation is provided by the refrigerant itself, which makes the refrigerant cooler.
Another function of the expansion valve is to adjust the amount of superheat. As stated before, the two-phase refrigerant is completely evaporated by entering the evaporator and absorbing heat from the water (it should be noted that during the evaporation process the temperature of the refrigerant remains constant and the absorbed heat is used as the latent heat required for the evaporation of the refrigerant not increase in temperature). Then, by absorbing more heat, the temperature of the vapor refrigerant also increases, which is called superheat vapor.
The amount of superheat is actually the difference between the temperature of the refrigerant entering the evaporator and the temperature leaving the evaporator. In compression chillers, adjusting the amount of superheat is very important in two ways.
- If the liquid enters the compressor, the internal parts are at risk and the operation of the compressor is disturbed. Therefore, it is always necessary that the refrigerant exiting the multi-degree evaporator is superheated to ensure that there is no liquid refrigerant in the evaporator exit.
- Part of the refrigerant coming out of the evaporator is used for cooling the compressor coils. Therefore, if the amount of superheat of the refrigerant increases, there is a possibility of burning these coils. Therefore, the maximum allowable superheat is 10 degrees Kelvin.
By opening and closing the flow path, the expansion valve controls the amount of refrigerant entering the evaporator and controls the temperature difference between the inlet and outlet. There are two types of expansion valves in compression chillers, which are:
Mechanical expansion valve:
The mechanical or thermostatic expansion valve, with the help of a temperature sensor that is installed at the outlet of the evaporator, determines the required flow rate of the evaporator.
Electronic expansion valve:
These valves also give the flow path by measuring the temperature and pressure of the refrigerant at the exit of the evaporator with a low and high command controller. The accuracy of electronic expansion valves is much higher than mechanical valves.
Evaporator of compression chillers
Evaporator is actually the last equipment in the cooling cycle that the refrigerant enters after passing through the expansion valve and exchanges heat with water. Usually, two types of evaporators are used in compression chillers.
Shell and tube evaporator
One of the most common heat exchangers used in a compression chiller as an evaporator is a shell and tube heat exchanger. This converter consists of a number of tubes placed inside a cylindrical shell. Shell and tube evaporators are offered in two types of dry and submerged expansion. The dry expansion evaporator is more popular due to the easier construction technology. In the dry expansion evaporator, the refrigerant coming out of the expansion valve is inside the evaporator tubes and the water is inside the shell. In general, in shell and tube exchangers, the wall of the tubes is considered as the heat transfer surface, and the heat is transferred between the two fluids through these surfaces.
Plate evaporator
Another type of heat exchanger that is used as an evaporator in compression chillers, especially mini chillers, is a plate evaporator. This evaporator consists of a number of plates that are placed at a small distance from each other. Hot and cold fluid flow alternately between these plates. The advantage of these evaporators is that the fluid spreads over the entire surface of the plate and the heat transfer level is much higher than the previous model. For this reason, for a certain amount of heat exchange, plate evaporators are much smaller than shell and tube evaporators.
مزایای چیلر تراکمی
- The ability to manufacture in all kinds of refrigeration tonnages for use in air conditioning and industrial refrigeration
- Lower price compared to absorption chillers
- Variety of products and compatible with all types of weather and climatic conditions
- The possibility of creating sub-zero temperatures in industrial projects
- Long life and low maintenance and service cost
- پشتیبانی تعمیرات و تامین قطعات در ایران برخلاف سایر دستگاههای تبرید
نکات نصب و راهاندازی چیلر تراکمی
- Both models of compression chiller need to design and build a suitable substructure on the roof before installing it on site. (A foundation that can withstand the weight and vibrations of the air-cooled chiller and the cooling tower.)
- Designing and implementing the circuit of chilled water pipes, from the chiller to the fan coils and the return piping line from the fan coils to the chiller.
- Design and implementation of piping to connect the condenser to the cooling tower in the water-cooled compression chiller.
فاکتور مهم در انتخاب چیلر تراکمی
- Climate
One of the important factors in choosing the type of chiller is the climatic and environmental conditions, which are divided based on the two factors of temperature and relative humidity. The climate is divided into 3 categories based on air temperature: tropical, temperate and cold, and based on humidity, it is divided into 3 categories: humid, temperate and dry.
The compression chiller designed for temperate regions cannot be used in tropical regions or, for example, in humid regions, the cold water compression chiller is a wrong choice. The following video explains the necessity of using a chiller that is designed according to the place of use.
- Account Type
The type and structure of the compression chiller is different based on the application. For air conditioning purposes, the chiller is only used in the hot months of the year and in limited hours, as a result of which the depreciation of the device and the cost of maintenance will be lower and it will have a longer life. But industrial compression chillers work in more hours and as a result will have more depreciation and a shorter lifespan. Even the chillers that are used in halls, laboratories and industrial centers for air conditioning and cooling also have a different structure from the chillers used in residential buildings.
- Refrigerating capacity
One of the important factors in choosing the type of compression chiller is the required refrigeration capacity. The cooling load calculation method is different for air conditioning and industrial uses (equipment cooling and process cooling). Based on thumb calculations, the cooling load in residential buildings is according to the table below.
|
climate |
Required cooling capacity |
|
cool |
Every 40 square meters, one ton of real cooling |
|
mild |
Every 30 square meters, one ton of real cooling |
| Tropical |
Every 20 square meters, one ton of real cooling |
چیلر تراکمی باردصنعت
Baredsanat production group, with expertise in designing and producing all kinds of air conditioning and cooling systems, has the ability to design and produce all kinds of compression chillers in two types of water-cooled and air-cooled in different capacities, according to the needs of our dear customers. All Bardsanat compression chillers are provided with a valid 5-year warranty, including all equipment and accessories, as well as 10 years of after-sales service. The equipment used in the chillers of this collection is from the world’s famous and reputable brands, among which the following can be mentioned:
- Compressor from BITZER Germany, HANBELL Taiwan and COPELAND USA
- Electronic expansion valve from CAREL Italy
- Miniature and thermal switches and device power from the German SIMENS brand
Other technical specifications of Bard Sanat compression chillers can be checked by type on the compression chiller purchase page. If you intend to buy a compression chiller for air conditioning use, you need to buy a fan coil along with the chiller. Bared Sanat is also a fan coil manufacturer in Isfahan. Contact us to get the compression chiller price and fan coil specifications.
روفتاپ پکیج چیست؟
Rooftop package is an equipment for cooling, heating and air filtration. As its name suggests, this unit is installed on the roof and works as an independent and complete unit for cooling and heating the building. Rooftop package is one of the most common air conditioning equipment used in office and commercial buildings, but it is not often used in residential buildings, the reason for which will be explained in the rest of the article. It should be noted that although the dual-purpose model of the rooftop unit is capable of providing heating as well, in Iran it is usually used to produce cool and comfortable air (in fact, it is a combination of a condensing unit and an air conditioner).
اجزای اصلی روفتاپ پکیج
The main components of the rooftop package are the compressor, air-cooled condenser, blower fan, DX coils and air filter, all housed in a large metal body. Of course, there are other components in the rooftop unit, some of their features are:
- A strong body that does not suffer from direct and constant sunlight and wind. In addition, the body should be insulated against the penetration of rain and snow.
- The rooftop package is connected to a ducting system and transfers cool air through the ducts into the building.
- On one side of the body, there is a vent for outside air to enter the package. This compartment is equipped with a cap that prevents rain and snow from entering the unit.
- Some rooftop packages are equipped with dampers to control the volume of air entering and leaving. The position of these dampers can determine the amount of outside air entering.
- Inside the unit and after the air inlet valve, a filter was placed to absorb dust, to prevent dust particles from entering the mechanical equipment, fans and channels. If there is no filter inside the rooftop, due to the deposition of dust from the outside air inside the equipment and channels, the efficiency of the device will decrease and eventually the device will have a major problem.
- In some units, there is also an air humidity adjustment device.
- A number of coils are placed in the rooftop units after the filter. These coils, which can be cold or hot or both depending on the type of rooftop package and its use, are used for cooling or heating the outside air.
- The fan installed inside the unit, which is usually of the centrifugal type, is placed after the coils and draws the outside air into the unit so that the air after passing through the damper, filter and coil enters the channel and spreads inside the building.
- The size of the cooling components of the unit, i.e. fan, condenser, compressor and controllers are usually installed at the back of the unit.
انواع روفتاپ پکیج
Rooftop packages are divided into 4 categories based on the type of air used for cooling.
Rooftop package with 100% fresh air
In this model, which is the simplest type of rooftop unit, the air that undergoes cooling and conditioning is completely supplied from the air outside the building, and the air inside the building is not included in the re-cooling cycle. But usually, to adjust the air pressure inside the building, part of the air is blown to the outside environment through the return channels.
Rooftop package with 100% return air
In some rooftop packages, the return air from the building is used and circulated. In this case, a damper is seen at the end of the return air channel. Using the return air from the building and combining this air with fresh outside air and performing operations on the combination of these two airs reduces the amount of energy consumption. If the unit is dual-purpose and used for heating, this reduction in energy consumption will be very significant in the winter season. The position and degree of opening and closing of the dampers determines the ratio of mixing of these two airs. Of course, it is necessary that a minimum amount of fresh air enters the system from the outside, and the dampers of the outside air will never be 100% closed. Otherwise, the indoor air quality will decrease due to the increase in carbon dioxide concentration and the air will become unhealthy for the people inside the building.
Rooftop package with 100% mixed air
The third type of units is designed in such a way that part of the air returned from the building passes through the damper and circulates, and another part is transferred outside the building. 3 Factors of outdoor air temperature, temperature and carbon dioxide level of the returned air determine the ratio of mixing of the two airs with each other and determine how many percent of the returned air should be transferred outside the building. In these cases, if the outside air temperature is close to the desired temperature of the building, all the volume of returned air from the building is transferred outside and does not circulate.
Rooftop package equipped with heat recovery
After entering the unit, the returned air from the building passes through a filter to get rid of pollution and suspended particles. Then it hits the heat recovery fins and causes the temperature of the fins to change. The heat recovery vanes also rotate towards the top where there is fresh air and cause the temperature of the fresh air to change. In fact, the returning air from inside the building gives its heat or cold to the vanes, and the vanes give this energy to the fresh air. In this method, the fresh air is preheated or precooled and then transferred to the heat transfer coils. This method has a significant effect in reducing energy consumption.
نحوه کار روفتاپ پکیج
- The filtered air (which, depending on the rooftop model described above, can be only fresh air from outside the building or a combination of fresh air and return air from the building) passes over the evaporator coils.
- Inside the evaporator coils, the cold liquid refrigerant is evaporating at low pressure. As a result of heat transfer in the evaporator, the air is cooled and transferred into the building through the channel. On the other hand, the refrigerant turns into steam due to air heat absorption and leaves the coils.
- The vapor refrigerant enters the compressor and its temperature and pressure increase. At this stage, the high-pressure refrigerant and superheat enters the condenser coils.
- Refrigerant heat is absorbed and transferred to the air through the body of the coils and the fins connected to the coils. As a result of this heat transfer, the temperature of the refrigerant decreases and turns into a liquid.
- The liquid refrigerant coming out of the condenser passes through the expansion valve and as a result of the expansion, it faces a decrease in pressure and a further decrease in temperature and again enters the evaporator coils to cool the air.
- Rooftop packages are usually controlled by a simple thermostat. The high refrigeration cycle continues until the building temperature reaches the thermostat setting
- If the rooftop is used to supply hot air in the winter season, it is necessary to transfer hot water from the engine room or the wall package device to the coils of the unit.
کاربرد روفتاپ پکیج
- The filtered air (which, depending on the rooftop model described above, can be only fresh air from outside the building or a combination of fresh air and return air from the building) passes over the evaporator coils.
- Inside the evaporator coils, the cold liquid refrigerant is evaporating at low pressure. As a result of heat transfer in the evaporator, the air is cooled and transferred into the building through the channel. On the other hand, the refrigerant turns into steam due to air heat absorption and leaves the coils.
- The vapor refrigerant enters the compressor and its temperature and pressure increase. At this stage, the high-pressure refrigerant and superheat enters the condenser coils.
- Refrigerant heat is absorbed and transferred to the air through the body of the coils and the fins connected to the coils. As a result of this heat transfer, the temperature of the refrigerant decreases and turns into a liquid.
- The liquid refrigerant coming out of the condenser passes through the expansion valve and as a result of the expansion, it faces a decrease in pressure and a further decrease in temperature and again enters the evaporator coils to cool the air.
- Rooftop packages are usually controlled by a simple thermostat. The high refrigeration cycle continues until the building temperature reaches the thermostat setting
- If the rooftop is used to supply hot air in the winter season, it is necessary to transfer hot water from the engine room or the wall package device to the coils of the unit.
مزایای استفاده از روفتاپ پکیج
Rooftop package units have advantages over split systems, which include:
- Less noise pollution in the building
- Small dimensions and less space required
- Increased efficiency due to the reduction of connections and pipe lengths
- The price is lower than the total cost of buying a chiller and air conditioner
- Easy installation
- Easy repairs
معایب روفتاپ پکیج
In this system, it is not possible to adjust and control the air temperature for each space independently, and this is a major flaw in these units; Because people in different spaces have different temperature needs, for example, if a building has 3 rooms, the comfortable temperature in one of the rooms is 24 degrees, another is 20 degrees, and the other room is 18 degrees. Now, if the temperature of the thermostat is set to the lowest value, then in the rest of the spaces, we have a waste of energy and people’s dissatisfaction. If the average temperature is considered, we also have people’s dissatisfaction and energy waste, and if the thermostat is set to the highest temperature, there is no energy waste, but people in the other two spaces are dissatisfied with the heat of the air. Therefore, rooftop packages are usually used in one-piece spaces (one hall or two parts).
Baredsanat production group started its activity in Isfahan in 2013 in the field of designing and producing all kinds of air conditioning and cooling systems. This collection has the ability to design and produce specialized types of rooftop packages in various capacities, according to the needs of our dear customers. All rooftop packages of this collection are provided with a valid 5-year warranty, including all equipment and accessories, as well as 10-year after-sales service. Some of the rooftop unit equipments are imported, which Baredsanat always tries to supply these equipments from the best and most reliable brands, among which the following can be mentioned:
- Compressor from BITZER Germany, HANBELL Taiwan and COPELAND USA
- Electronic expansion valve from CAREL Italy
- Miniature and thermal switches and device power from the German SIMENS brand
- Condenser fans of axial type and Zilabag, Rosenberg and IBM brands.
All other equipments are made by Bared Sanat company and are of excellent quality and at the level of reputable European brands. The price of Baredsanat rooftop units varies based on the type of capacity and the brand of equipment used. You can contact the experts of the collection to get the exact price.
