【 Weak current College 】 expansion valve installation and matching

1. matching:
According to R, Q0, t0, tk, liquid pipelines and valves of resistance losses, steps:
1.1 determines the expansion valve pressure difference on both sides; determine valve; select valve models and specifications;
1.1.1 determine valve at both ends of the pressure difference: Δ P = PK-Σ Δ P o I-P (KPa) (1) type: PK-condensing pressure, KPa, Σ-Δ P I to Δ Δ P P 1 + 2 + 3 + Δ Δ P P 4 (Δ P 1 for liquids pipeline pressure loss; Δ P 2 elbows, valves, etc. have resistance losses; Δ P 3 is the liquid pipe pressure loss, rising to Δ P 3 = ρ ɡ h; Δ P 4 to knock head and knock resistance loss capillary is usually different to 0.5bar); Po-evaporation pressure, KPa.
1.1.2 determine valve: select out-of-balance within the balance or, from the evaporator pressure drop. On R22 systems, when the pressure exceeds the evaporating temperature 1 ° c, are advised to use exdpansion valve.
1.1.3 select valve types and specifications: according to the calculation of Q0 and expansion valve before and after Δ P and evaporation temperature t0 the relevant table found valve model and valve capacity.
In order to simplify the matching process, you can also press design techniques, now with thermostatic expansion valve of the model and specifications, must be based on the refrigeration system and the type of refrigerant evaporating temperature range and evaporator heat load size, options should be consistent with the following requirements:
(1) the choice of thermal expansion valves capacity than the evaporator of the actual thermal load large 20-30 per cent; (2) no cooling water control valve or winter cooling water temperature lower refrigeration system, select the thermostatic expansion valve, the valve size should be larger than the evaporator load of 70-80 per cent, but the maximum of evaporator heat load of 2 times;
(3) select thermal expansion valves should be calculated for the pressure drop of liquid pipeline to produce valve pressure difference before and after, then according to the manufacturer of the expansion valve calculation capacity table to determine the specifications of the thermostatic expansion valve.
2, installation:
2.1 pre-installation checks whether it is good, especially thermal body parts;
2.2 installation location must be in a place near the evaporator, the valve should be installed vertically, not tilt or reverse the installation;
2.3 installation, you should be aware of the heat sector remains in the liquid, temperature sensor, the sensor should be installed than lower valve body;
2.4 as possible sensor installed in the evaporator of export levels back into the trachea, the General should stay away from the compressor suction port 1.5m above;
2.5 sensor must not be placed with effusion of the pipeline;
2.6 if the evaporator outlet with a gas-liquid exchanger, generally will heat the packaging in the evaporator, the heat exchanger outlet;
2.7 sensor usually placed in the evaporator return gas pipe, and close to the tube walls wrapped tightly, contact should be clean, oxide-exposed metal qualities;
2.8 when the return gas pipe diameter smaller than 25mm, the sensor can tie back to the top of the trachea; when the diameter is greater than 25mm, in back to the underside of the trachea 45 ° at the bottom of the pipe, to prevent the accumulation of oil and other factors that influence the correct sensor temperature sensor.
3. debugging:
3.1 evaporator outlet located thermometer or use inspiratory pressure to check superheat;
3.2 superheat is too small (for fluid is too large), adjustable lever clockwise turning half-ring or a ring (that is, increase the spring force, reducing valve to open degree), when the refrigerant flow reduction; adjusting Rod thread a rotating coils should not be too much (adjustable Rod thread turning in a circle, superheat is about changing the 1-2 ° c), after repeated adjustments until meet the requirements;
3.3 experience regulating means: rotation adjustment Rod thread to change the valve to open degree, make the return gas pipe outer corresponded frosting or condensation. On evaporation temperature below 0 degrees of refrigeration equipment, if frosting with touch, there is a way to hand the cold feeling stuck, this time opening suitable; evaporation temperature above 0 ° c, depending on the circumstances of dew condensation.