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Here is the professional translation of the provided content into English, incorporating key technical terms and maintaining clarity for refrigeration industry applications:

Expansion Valve Selection Guide

The throttling device is a fundamental component in refrigeration systems, serving three critical functions:

1. Regulating pressure differential between high and low sides
2. Controlling refrigerant flow rate
3. Maintaining optimal superheat in the evaporator

The performance and reliability of throttling components significantly impact system operation. Oversupply of refrigerant may cause liquid floodback or compressor slugging, while insufficient flow leads to reduced evaporator efficiency, lower cooling capacity, and excessive superheat. Therefore, precise selection is essential.

I. Common Throttling Devices

Commercial/industrial systems primarily use:

• Thermostatic Expansion Valves (TXV)
• Electronic Expansion Valves (EEV)

Selection factors include refrigerant type, pressure differential across the valve, flow capacity, and required superheat. Note: Valve sizing must be based on evaporator capacity, not compressor capacity.

II. TXV Selection Procedure

Refrigerant Identification
Determine refrigerant type (e.g., R22, R134a, R404A, R507, R407C, R410A) as material compatibility and pressure characteristics vary14.

Design Temperatures
Establish evaporating temperature (T_e) and condensing temperature (T_c), which define corresponding pressures (P_e and P_c)46.

Pressure Drop Calculation
Total pressure drop (ΔP) across the valve includes:

• P_c: Condenser outlet pressure
• P_e: Evaporator inlet pressure
• ΔP₁: Liquid line friction loss (pipes/fittings)
• ΔP₂: Elevation pressure loss (ΔP=ρgh)
• ΔP₃: Distributor/capillary tube drop (~1 bar)36.
  For flash gas economizer systems, include additional high-side losses.

Subcooling Determination
Account for system subcooling at the valve inlet, which affects capacity (use correction factors from manufacturer charts)6.

Capacity & Superheat Validation
Select valve capacity to match evaporator load at design superheat (typically 4–8K)4.

Valve Type Selection

• Internally Equalized TXV: For evaporators with pressure drop <0.3 bar (e.g., short-tube coils)26.
• Externally Equalized TXV: Required for high-pressure-drop systems (e.g., long pipelines, distributors)46.

III. Stability Considerations

• Load Ratio Range:

• TXV: 30%–100% (below 30% may cause hunting)34.
• EEV: 10%–100%, preferred for variable-speed compressors3[8].
  • Example: A -18°C cold storage system with 5.8kW (peak) and 1.7kW (steady) loads risks TXV oscillation at low load. EEVs resolve this via precise step-motor control3[8].

IV. Comparative Analysis

V. Installation Notes

• TXV Bulb Placement: Mount on horizontal suction line, avoiding oil accumulation zones46.
• Superheat Adjustment: For TXVs, rotate stem incrementally (¼-turn intervals)4.

Supplementary Data from Search Results

• Electronic Expansion Valves:

• Type UKV (bidirectional, C_v: 0.015–1.15) and PKV (for -50°C, C_v: 0.05–0.27) suit diverse applications1.
• CO₂ systems require high-pressure valves (e.g., UKV-J, MOPD 10MPa)1.
  • Software Tools: Emerson and Kale provide valve selection software for precise matching3.

For full technical specifications, refer to manufacturer datasheets136.

This translation adheres to industry standards while integrating contextual data from search results. Let me know if you need further refinements.

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1. The large blue PCB on the right is the drive mainboard for chiller compressor, equipped with power modules and transformers to supply power and control signals for variable-speed compressor.
2. The original McQuay touch screen held on left hand connects to the mainboard via communication cables. Its display shows compressor operation interface to read real-time operating parameters and fault codes, verifying program and signal output after component repair.
3. External power cables simulate on-site power supply for power-on testing, to confirm full functions of the repaired board for magnetic levitation / variable-frequency centrifugal compressor central air-conditioning unit.

1. The high-precision DC regulated power supply on top supplies adjustable power to the blue PCB drive board at right, with real-time output voltage of 24.4V displayed to simulate actual unit power supply condition.
2. The touch screen on desktop connects to debugging software which displays compressor parameter panel, for reading operating data and fault codes of the control board.
3. With probes, tweezers and multimeter, the technician tests voltage and signal of electronic components to fix short-circuit or damaged chips like IGBT and MCU; final power-on simulation test will be carried out after maintenance.
4. This PCB is core electronic control part matching Danfoss magnetic-bearing & scroll variable-speed compressors for chillers and large central air-conditioning systems.

1. A precision PCB main control board is laid out in front of him, with maintenance tools including a multimeter, DC regulated power supply, solder and maintenance fixtures arranged on the workbench.
2. With desk lamp illumination, he inspects circuits and electronic components by hand, using testing instruments to measure voltage and continuity to locate short circuits or faulty parts on the board.
3. Such circuit boards serve as drive controllers for magnetic levitation / variable-frequency compressors, falling into the category of electrical maintenance for refrigeration equipment.

1. Product Information

Brand: Danfoss, Denmark (Danfoss logo cast on valve body) Common Models: ETS250, ETS250L, ETS400; part codes: 034G2601, 034G3500. This is solder-type version with copper tube ends for brazing connection. Structure: Y-shaped brass valve body plus top stepper motor actuator. The yellow cap protects the wiring terminal for connecting control cables; the side threaded port is reserved for service pressure testing and oil filling.

2. Application & Working Principle

Application: Large central air conditioning systems, screw/scroll chillers and industrial refrigeration units. It is original matching component for chillers of Carrier, York, McQuay and other famous brands. Function: Driven by stepper motor, it adjusts valve opening accurately to control refrigerant flow into evaporator. It replaces conventional thermostatic expansion valve for higher precision of electronic temperature control. Bi-directional flow available; full close position completely cuts off refrigerant circuit with the same shut-off performance as solenoid valve.

3. Installation Features

Two-end copper pipe connections are designed for on-site brazing with refrigeration copper tubing. Red plastic caps on pipe ends are factory dust-proof plugs. It is high-capacity throttling component for commercial refrigeration.

1. Nameplate Specifications

Actuator: DC 12V, 0.5A, Rated Power 6.0W Max Working Pressure: 34 bar (493 psig). Made in Denmark with CE certification.

2. Construction

Y-shaped brass valve body. The yellow top cap covers the wiring terminal of the stepper motor. Both ends are copper stubs for brazing connection, and the side threaded port serves for service pressure measurement.

3. Application

Core throttling component matching screw/scroll chillers, large central air conditioning and industrial refrigeration units, widely fitted on chillers of Carrier, York, McQuay and other mainstream brands.

4. Functions

Electronically driven by stepper motor to precisely regulate refrigerant flow as replacement of conventional thermostatic expansion valves. Bi-flow available; fully closed position shuts off refrigerant completely, performing the cut-off function same as a solenoid valve.

5. Installation

Copper tube ends are designed for on-site brazing; red plastic caps on pipe ends are factory dust protection plugs.