(1) Selection of evaporative cooling water-cooled environmental protection air conditioning (air cooler) equipment
"Meishuo Wind" evaporative cooling water-cooled environmental protection air conditioner has three series: axial flow independent water supply evaporation cooling water cooling environmental protection air conditioning, axial flow central water supply evaporation cooling water cooling environmental protection air conditioning, centrifugal evaporation cooling water cooling environmental protection air conditioning. Axial flow type independent water supply evaporation cooling water cooling environmental protection air conditioning series can choose plastic shell or stainless steel shell, beautiful design, the main engine comes with float water level control system, pumping pump and drainage pump, compact structure, suitable for small places; Axial central water supply evaporation cooling water cooling environmental protection air conditioning series can choose plastic shell or stainless steel shell, beautiful design, the use of external central water supply system, cost-effective, suitable for large industrial plant workshop overall ventilation and cooling; Centrifugal evaporation cooling water-cooled environmental protection air conditioning series adopts centrifugal fans, whose air volume and indenter are higher than those of axial flow series, and the air supply distance is farther, which is suitable for large places such as steel frame structures, empty factories and commercial crowded places to cool down. The specific air cooler equipment selection should comprehensively consider the space size of the use place, personnel density, heat generation and installation location and other comprehensive factors to select the appropriate series and models.
(2) Use enthalpy wet map to determine the supply air temperature
First of all, according to the local meteorological conditions, the outdoor status point W is determined on the enthalpy map, and the relative humidity line along the isoenthalpy line from the W point is intersected at the O point at 85% (the saturation efficiency of the cooler), and the temperature corresponding to the O point is the temperature t0 of the supply air. The moisture content (g/kg ? dry) of the air outlet can also be detected from the O point, which can be used to calculate the humidification of evaporative air coolers.
(3) The choice of the number of air cooler equipment
1. Full ventilation
(1) Calculate according to theory
According to the conventional air conditioning load calculation formula to find out the cooling load and wet load and supply air volume of the use of the room, and then calculate the total cooling capacity that the air cooler can provide, in order to select the number and model of the air cooler, the total cooling capacity of the selected air cooler must be greater than the cooling capacity required by the use of the room, and the margin can generally be considered by 10%. Theoretical calculation of the total cooling capacity of the evaporative air cooler:
Total cooling capacity S=LρCp{e?(tg-ts)+tn-tg}/3600
Where: L------ the actual supply air volume of the air cooler (m3/h)
Density of air in the air outlet ------ ρ (kg/m3)
Cp------ air specific heat (kJ/kg?K)
e------ the saturation efficiency of the air cooler, generally take 85%
(tg-ts) ------ wet and dry bulb temperature difference (°C)
(tn-tg) ------ indoor and outdoor temperature difference (°C)
Set △t1=(tg-ts), △t2=(tn-tg), where △t1 is positive and △t2 has positive and negative values.
The total cooling capacity S = LρCp (e?△t1+△t2), where ρ, Cp, e are constants, from which it can be seen that the size of the total cooling amount of the air cooler is related to the actual air output of the cold air blower, the temperature difference between the wet and dry bulbs, and the temperature difference between indoor and outdoor. Since △t1 and △t2 are uncertain quantities, they change with the temperature of the external environment, so the formula for total cooling is generally only used for qualitative analysis, and less used in quantitative calculations. According to the characteristics of "Meishuo" evaporative air cooler, we commonly use experience to calculate the number of equipment.
(2) Empirical calculation
The number of air exchanges is used as a parameter to determine the number of air coolers required in a certain space, which is a common design method for evaporative air coolers. This approach is generally used in actual engineering designs.
(1) Definition of the number of air changes: the number of air changes N (times / hour) = the total air supply volume of the refrigeration space L / (indoor area S× the height of the air supply port and the exhaust port H);
(2) The general environment requires 25 to 30 times of ventilation times/hour;
(3) Public places with dense traffic require 30 to 40 times per hour of ventilation;
(4) The production workshop with heating equipment requires more than 40 to 50 times/ hour of air exchange;
(5) The number of air changes in the humid southern region is appropriately increased, while the hotter and drier northern region can be appropriately reduced.
Specific calculation steps:
(1) Calculate the area to be cooled in the project S, determine the largest height of the transmission or exhaust outlet H, and then calculate the volume V of the refrigeration space;
(2) Determine the number of air changes N according to the actual situation;
(3) The volume of the cooling space V× the number of air changes N, to obtain the total supply air volume required for the space L;
(4) The total supply air volume is divided by the actual air volume L1 of the selected single air cooler, that is, the number of required air coolers is obtained n.
2. Post air delivery
The above is the general design calculation method of comprehensive air supply, but in many cases, some commercial and industrial buildings have a high temperature in some areas, such as machine heating, processing heating, etc., often in this case, the indoor temperature is higher than the outdoor temperature, and the evaporative air cooler can cool the outdoor air and continuously deliver it indoors. For example, there is a factory workshop whose equipment generates a high amount of heat, with indoor temperatures of up to 45°C and outdoors of only 38°C. The evaporative air cooler can cool the outdoor air at 38 °C to below 30 °C and send it into the room, which is 15 °C lower than the original indoor 45 °C, which can significantly improve the working environment. In this case, we generally do not calculate the heat load, only need to design a set of post air supply system, the air outlet continues to send cold air to the post, and the hot air around the post is continuously dispersed. In addition, the post air supply system can also be used in some completely open spaces, and these places consider post cooling as a more appropriate choice.
Determination of post air supply air volume: According to the actual situation of the post, first determine the air volume of each post, and multiply the required air volume of each post by the number of posts to find the total air supply volume required, and then the number of air coolers that should be selected can be calculated. The air volume of each air outlet is determined according to the actual situation, but in general, the air volume of the air outlet is controlled as much as possible between 3 and 6m/s (according to the heat generation and personnel density of the installation site).
3. Determination of exhaust air volume
"Meishuo" evaporative air cooler is to continuously inject fresh cold air into the room to replace the indoor turbid air and achieve the purpose of cooling, so the basic form of the "Meishuo" cold air cooling system is "one in and one out", rather than closed. In general, the indoor positive pressure is used for natural exhaust, and mechanical exhaust can be used in a confined space. In order to achieve a good ventilation and cooling effect, the exhaust air volume of the "Meishuo" cold air cooling mechanism cold system should reach more than 80% of the total supply air volume, and the speed of natural exhaust should be controlled within 2m/s to ensure the good operation of the system.
(4) Design of ventilation ducts
1. Basic terminology
(1) Air volume
Method for calculating the air volume by round duct cross-section:
L=900лd2v （m3/h）
In formula d------ the inner diameter of the duct (m)
v------ Wind Speed (m/s)
Duct calculation method by rectangular duct:
L=3600abv （m3/h）
Where a, b------ duct section net width and net height (m)
(2) Duct system resistance
Duct system resistance includes two parts: frictional resistance along the way and local resistance, which are expressed as follows:
△P=△Pm+△Pj
Where △P----- system total resistance (Pa)
△Pm----- system frictional resistance along the path (Pa)
△Pj----- system local resistance (Pa)
(3) Calculation of frictional resistance along the system
△Pm=△pm?L
where △pm----- is the resistance along the path per unit length (Pa/m)
Length of L----- pipe segment (m)
(4) Loss of local resistance of the system
△Pj=ξ?v2ρ/2
where ξ ------ local resistance coefficient
v------ Air velocity (m/s) at the place where this pressure loss occurs in the duct
ρ------ Air Density (kg/m3)
2. "Meishuo Wind" air cooler piping system design points
(1) The material of the supply air pipe is generally galvanized sheet, and the double-sided aluminum foil phenolic composite duct, the single-sided color steel phenolic composite duct, the plastic duct and so on can also be used.
(2) The air outlet is set in the place where the actual need to cool down, the air outlet design air volume is the air supply volume required for the occasion to cool down, the air outlet specifications can be determined according to the air volume and the air outlet speed, the air outlet material can be made of aluminum alloy products or plastic and other products, the air outlet type can be used in various forms according to the actual situation, but it is recommended to choose a DC type single-layer or double-layer louver air outlet, the average flow rate of the air outlet throat is controlled at 3 to 6m/s, and the flow rate of 4~5m/s is recommended; It is recommended to install an air outlet control valve at the air outlet to facilitate air volume adjustment.
(3) The specifications of the supply duct are generally designed by the method of assumed flow rate, the wind speed of the main duct is maintained at 6 ~ 9m / s, the branch duct is 4 ~ 6 m / s, and the air speed in the end pipe of the system should be maintained at 3 ~ 5 m / s.
(4) Air volume (M3/h）=πr2 × duct wind speed (≤14m/s) ×3600
(5) In principle, the designed duct system requires both economical and minimum system wind resistance and noise, so that the "Meishuo" air cooler supply air volume as much as possible. The radius of curvature of the duct elbow is generally not less than 1.5 times the width of the pipe bend to reduce the system resistance.
(6) According to the characteristics of the wind pressure of each series of "Meishuo Wind" series of cold air blowers, the pipes of the air supply system should not be designed too long, and the layout can not be used in the place where the duct is not used, and the duct must be used, and the duct should be designed to a shorter route as much as possible.
(7) The designed pipeline should be as straight as possible to avoid unnecessary bends and branches to reduce the loss of local resistance of the system pipeline.
(8) The outdoor air duct must be waterproof and leak-proof measures, the outdoor air duct of the side wall installation unit must be set with a certain outward slope, and the outdoor air duct of the roof installation unit must be waterproof measures.
(9) The longer pipe is designed into a multi-section duct with different specifications according to the different air volume, and the reducer pipe is connected, the reducer pipe setting should not be too much, the general whole system should not exceed four, and the length of the reducer pipe ≥ 2 (D-d) to determine.
(10) The connection between the air supply pipe and the air cooler should be softly nozzled or flanged, and the outdoor air supply pipe is best designed to be insulated, and the indoor generally does not need to be insulated.
(11) If there is a branch pipe in the design, it is necessary to install a valve or wind baffle on the branch pipe to adjust the air volume, so that the air volume of the branch pipe meets the design requirements.
(5) Airflow organization
The air flow organization form here refers to the flow pattern formed by the flow of air flow in the room. There are many forms of airflow organization, which should be reasonably selected according to the requirements of the use of space, combined with the characteristics of the building structure and the layout of process equipment. According to the interrelationship and air flow direction of the position of the feed and exhaust outlets, the commonly used air flow organization is: side-feeding side-row, side-sending discharge, upper-sending side-row and upper-sending discharge, and the actual project may be a combination of several airflow forms.
1. Side-feed side row
The side-feed side row method of sending and exhausting air outlets are arranged on the side of the room, and according to the span of the room, it can be arranged into a one-sided transmission one-sided row and a double-side transmission double-side row. This method is suitable for installing air coolers on side walls, which have windows for natural exhaust or mechanical exhaust for side wall installation.
2. Side-by-side line
The air supply outlet of the side feed method is located on the side of the room, and the air outlet is placed in the upper part of the room. This method is suitable for installing coolers on side walls, with skylights on the roof for natural exhaust or roof installation for mechanical exhaust.
3. Upper send side row
The air outlet of the upper side row is located in the upper part of the room, and the exhaust air outlet is placed on the side of the room. This method is suitable for installing air coolers on roofs, with windows on the side walls for natural exhaust or for mechanical exhaust for side wall installations.
4. Send up the line
The air supply port of the upper feed side row is located at the top of the room, and the exhaust air outlet is also placed at the top of the room. This method is suitable for installing air coolers on the roof, only the roof has a skylight for natural exhaust or roof installation mechanical exhaust.
(6) Water supply and power supply
(1) Use a clean water source (generally municipal tap water) and ensure that the pressure of the water source ≥ 1.0kgf/cm2.
(2) A shut-off valve should be set up near the inlet pipe (DN15) of the air cooler, and a water pipe fitting should be reserved for cleaning.
(3) In order to prevent the rise and cracking of the water supply pipeline in winter, the outdoor water supply pipe of the cooler must be equipped with a thermal insulation and drainage valve (determined according to the local water supply and drainage design code), and the water storage in the water tank in the unit must be drained when the cold air mechanism is not used in winter.
(4) Ensure that the power supply voltage is stable between single-phase 220~240V and three-phase 380~400V, and the current reaches the rated current specified by the nameplate of the machine.
(5) Air switches should be installed on the main circuit to avoid faults caused by short circuits, overloads, etc.
(7) Noise control
In general, the noise of the "Meishuo Wind" evaporative air cooler is relatively small, and the actual design process needs to consider the selection of a suitable air cooler series, while designing the air supply system, it is necessary to pay attention to the noise requirements of different places of use, the wind speed in the duct cannot be too large, and the materials used in the duct should meet the requirements. For example, the thickness of the galvanized iron duct should be required, and too thin will cause jitter and noise; When using mechanical exhaust, the suction outlet air velocity of the exhaust pipe should not be too large; There should be a soft nozzle at the junction of the air cooler and the air duct; The production and installation of the duct should meet the specifications, and measures such as vibration avoidance should be considered when special requirements are required.
(8) Explanation of the air outlet method
(1) DS means bottom outflow: BS means side air outlet: AS means top air.
(2) Water consumption description: The water consumption of all models is measured under the standard case of dry bulb temperature of 38 °C and wet bulb at 23 °C in the air inlet.
(3) According to the actual situation of the customer, a larger air volume model can be designed.
(4) If the parameters are subject to change without prior notice, please refer to the fuselage nameplate.
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