Monday, December 27, 2010
College】 【weak cold storage expansion valve debugging and troubleshooting techniques】..
<br> cold storage expansion valve debugging and troubleshooting techniques outlined in <BR> <BR> 1 is well known, thermal expansion valve refrigeration system is one of the four components in the system responsible for the reduced refrigerant evaporation pressure from the .condensing pressure, and. proportional control of refrigerant flow.. A thermal expansion valve system will directly affect the performance of the whole system, so the work of the thermal expansion valve and remove the fault and appropriate the right choice, the operational life of the .air conditioning system, cooling effect, is significant running costs ... <BR> 2 thermal expansion valve works. <BR> Thermal expansion valve is the export of gas through the feelings of the evaporator superheat of refrigerant into the evaporator to control .the flow of refrigerant. In accordance with the balance in different ways, thermal expansion valve into the outside. balance and internal balance, while in the central air conditioning system in the use of external balance. by inductive bodies, executive bodies as bodies and body .composition.. Work, fixed the export pipeline in the evaporator temperature on the sensor package of superheated evaporator outlet temperature, the pressure generated within the thermal package, spread to the diaphragm by the upper part of the capillary space in the diaphragm under pressure to be .flexible. Deformation of the way the signal is passed to the thimble (executive body), thus their valve opening to control the flow of refrigerant.. <BR> 3 Several thermal expansion valve failure analysis work <BR> 3.1 plug the thermal .expansion valve blockage causes failure <BR> 3.1.1 <BR> thermal expansion valve refrigeration system failure is frequent clogging, including. "fouling" and "ice block." fouling was mainly due to impurities present in the system ., such as welding slag, copper scrap, iron and fiber.. Ice block because the system contains too much water (moisture), moisture of the way there: <BR> 1) install the system in the vacuum of sufficient time, the .moisture inside the pipe can not exhausted;. welding pipe junction is not good, there are leakage points.. <BR> 2) charge in the refrigerant to the system, had not connected the hose to blow out the air hose.. < .; BR> 3) additional lubricant for the system, into the air.. <BR> 3.1.2 the location of blockage occurred <BR> general congestion occurs in the dry dirt on the filter, the system of impurities blocked by the .filter housing, causing the dirty block.. Occurs, the system first returns showed temperature increases, the superheat increases, after a serious failure, the system stops functioning, such as the system of impurities not removed, the system can no longer boot.. .Ice blockage generally occurs in the throttle at the expansion valve for example, because it is the lowest temperature of the entire system, where the smallest aperture.. Because the system is not cooling, the overall system temperature rise, as the temperature increased, the .ice will gradually melt at blocking, and then resumed cooling capacity of the system, with lower overall system temperature will occur again, the ice block.. Therefore, the ice jam is an iterative process.. <BR> 3.1.3 Remedy blocking .rule out blocking the breakdown <BR> So how do you do? For fouling, if not very serious, for a dry filter on it.. If it is very serious, he would re-clean the system of impurities in the pipeline, .vacuum, re-charging refrigerant.. For small ice block, hot towel available at the ice block, ice block if a more serious level, has affected the normal operation of the system, will have to replace the filter dryer, re-pipe at .the water out of the system, vacuum,. re-charging refrigerant.. <BR> 3.2 package temperature thermal fault <BR> 3.2.1 package common cause of failure occurs when the system <BR> expansion valve for the liquid .has been uneven or expansion valve does not close a small, superheat, subcooling is not correct, etc.. phenomenon. The reason may be the temperature package out of the failure.. Including: <BR> 1) temperature package capillary fracture, .the sense temperature of the filling material left out, resulting in not the correct signals to the thermal expansion valve enforcement agencies.. <BR> 2) temperature package wrapped position is not correct.. <BR> 3.2.2 Packet troubleshooting approach .temperature <BR> package temperature generally tried to keep the level of exports in the evaporator section of pipe on the back, away from the compressor suction port and close to the evaporator, but not vertical.. When the level back to the tracheal diameter .of less than 7 / 8 "(22mm) when the temperature package should be installed in the back to the top end of the trachea, the suction pipe of the" one o'clock. "Back when the level of tracheal diameter of .more than 7 / 8 "when. temperature package to be installed in the back tube axis and the horizontal axis of the following 45 degrees, the suction pipe of the" 3 o'clock "position.. Because the temperature package installed on the .upper part of the suction pipe will reduce the sensitivity of the reaction, may make too much refrigerant in the evaporator, the temperature package installed on the bottom of the suction pipe for the fluid can cause the disorder, because there are always a small amount of .liquid. temperature refrigerant flow to the location of installed packages, which led to the rapid temperature change in package temperature.. <BR> Installation, temperature of copper required to wrap up, back to the pipe surface to rust, if it is steel ., coated with silver paint after the surface rust to ensure the temperature package <BR> good contact with the back to the trachea.. Temperature package must be below the top of diaphragm valve chamber, and the temperature level of the package to be placed .on the head or down, when the relative position of the chamber above the diaphragm, the capillary tube should be bent into a U-shaped on, so the liquid into the diaphragm chamber ... To avoid the system suddenly shut down, liquid refrigerant .or oil product in the package where the level of temperature affect the pipe temperature performance of the package, temperature of the pipe <BR> should be made after the improper adjustment <BR> 3.3.1 3.3. on the expansion valve to adjust .the concept of <BR> said adjustment, we must first understand a few concepts (1) expansion valve superheat: the thermal expansion valve at a certain opening, as superheat corresponding to the earlier work of superheat. The thermal expansion valve superheat.. .Including static superheat (SS) and the opening superheat (OS).. <BR> (2) static superheat: the thermal expansion valve in the open position, the spring force of the smallest, when the thermal expansion valve superheat control of the .smallest, called static superheat SS.. <BR> (3) dynamic superheat: Kong Kaiqi expansion valve, the valve hole with the opening of the export steam superheat increases, far from the valve Kong Kaiqi to fully open, its value increased superheat .called dynamic. superheat OS.. <BR> 3.3.2 the correct expansion valve adjustment method <BR> (1) adjusting the thermal expansion valve, you must confirm the anomaly is due to cold storage refrigeration thermal expansion valve caused by deviation .from the optimal operating point, not because of low freon, dry. filter clogging, filters, fans, belts and other reasons caused.. Meanwhile, the temperature must ensure the correctness of packet sampling signal, temperature installation location must be correct, must not .be installed in the pipeline is below the bottom of the tube to prevent oil factors plot the correct temperature thermal package.. <BR> (2) thermal expansion valve adjustment note <BR> thermal expansion valve adjustment, and refrigeration equipment must be .carried out under normal operation.. The surface due to evaporation can not be placed thermometer, you can use the compressor suction pressure as the evaporator saturation pressure, evaporation temperature look-up table are approximate.. Measured with a thermometer the temperature back to the .trachea, compared with the evaporation temperature to check the superheat.. Adjustment, if the superheat was too small, you can adjust the screw to rotate in a clockwise direction (ie, spring force increases, reducing the thermal expansion valve opening degree), the .flow decreases; the other hand, if they feel too much superheat., that is less than for the liquid, you can adjust the screw to the opposite direction (counterclockwise) rotation, the flow rate increases.. As the actual work of the thermal .expansion valve thermal systems there is a certain amount of thermal inertia, lags behind the formation of signal transduction, stable operation before the next adjustment.. Therefore, the adjustment process must be patient and meticulous, adjusting a screw rotation number of cycles should not be .too fast.. <BR> (3) thermal expansion valve to adjust the specific steps <BR> 1) downtime.. The digital thermometer probe inserted into the mouth of the evaporator return air (corresponding to temperature package location) insulation layer ... The pressure gauge and connected to the compressor low pressure valve tee.. <BR> 2) boot, so the compressor runs more than 15 minutes into the steady state, the pressure indicator and temperature display to stabilize values.. < .BR> 3) read out the digital thermometer measured the temperature T1 and pressure gauge the temperature corresponding to T2, superheat is the difference between the two readings T1-T2.. <BR> Note must be read out of these two readings.. .Thermal expansion valve superheat should be between 5-8 ℃, if not, then make the appropriate adjustments.. Adjustment steps are: First, remove the protective cover of thermal expansion valve, then turn the adjustment screw 2-4 laps, and so the .system is stable, re-readings, calculate superheat, whether in the normal range, it is not, repeat the previous operation, until. meet the requirements, the adjustment process must be carefully detailed.. <BR> 4 thermal expansion valve < .; BR> 4.1 correct choice of the purpose of the thermal expansion valve thermal expansion valve <BR> matching the performance of the whole system plays an important role to play, the right choice will allow the thermal expansion valve to maximize the evaporator. utilized ., and to the evaporator and the heat load is always matched.. <BR> 4.2 thermal expansion valve and the system does not match does not match the phenomenon <BR> will make the refrigerant flow system has been uneven, leading to the .cooling capacity of thermal expansion valve when the big, sometimes small, when the cooling capacity is too small,. will lack the evaporator for the liquid, resulting in excessive heat, the system performance will be adversely affected. When the refrigerant when excessive, can .cause shock, intermittent over the evaporator for the liquid, leading to the compressor suction pressure. sharp fluctuations, and even liquid refrigerant entering the compressor, causing fluid strike (wet stroke) phenomenon. <BR> 4.3 <BR> selected based on .the refrigerant according to type of refrigeration system, evaporator and the evaporator superheat temperature range of the size of the load. choice.. <BR> 4.3.1 <BR> selection and the general procedure described below under the expansion valve to the .choice of method.. Because now with ceiling cooling fan, generally larger than the evaporation pressure drop, so are outside the balanced use of the thermal expansion valve.. According to the evaporation temperature and the thermal expansion valve of the pressure of import and export ., check the supplier to the product selection table. <BR> General steps are as follows: <BR> 1) determine the type of refrigerant system.. <BR> 2) to determine the evaporator evaporating temperature, condensing temperature and .cooling capacity.. <BR> 3) import and export of thermal expansion valve pressure difference.. <BR> 4.3.2 Example <BR> The company has one evaporator coil (4DW4/10F-50x50.3A), using .refrigerant R407C, cooling capacity of 96KW, evaporation temperature of 8 ℃, the condensing temperature is 50 ℃, select. What type of thermal expansion valve (in case of Danfoss products.). <BR> First determine the import and export expansion valve .pressure difference across the P Δ.. <BR> Formula: <BR> P k for the condensing pressure.. <BR> P 0 is vapor pressure.. <BR> 1 P Δ is the pressure drop for liquid .copper.. <BR> 2 P Δ as dispensers and sub-liquid capillary pressure drop.. <BR> P k (condensing pressure), P0 (evaporation pressure) from the known parameters given in the psychrometric chart in Richard.. .<BR> P k = 17.5 5 10 × P a, P0 = 6.5 5 10 × P a A) <BR> the copper tube for the fluid pressure drop, as the company uses coil selection software, in the calculated. data .for fluid tube has a pressure drop.. It is known 1 P Δ = 0.0031 5 10 × Pa.. Re dispensers dispense pressure drop brass to take empirical value 2 P Δ = 1 5 10 × Pa.. "G <BR> .; used as refrigerant R407C, cooling capacity of 96KW, evaporation temperature is 8 ℃, the condensing temperature is 50 ℃, 1 P Δ <BR> to 10bar, select the model TDEZ26 thermal expansion valve (Danfoss products to. example). < .; BR> Cooling Capacity (KW) <BR> evaporation temperature evaporation temperature +15 ℃ +10 ℃ <BR> pressure drop across the expansion valve △ P (bar) pressure drop across expansion valve △ P (bar). Type and .nominal cooling capacity <BR> 5 Conclusion <BR> stability and air-conditioning evaporator refrigerant outlet superheat, and therefore the exclusion of timely and accurate thermal expansion valve failure and the right choice and match the thermal expansion valve system. is very important .. <BR> Danfoss Expansion Valve: used to adjust the evaporator the liquid refrigerant in the supply of ~..