Danfoss expansion valves the

Types of Danfoss expansion valves

Danfoss expansion valves are small devices built to control refrigerant flow to the evaporator in cooling systems. They function by holding the proper pressure difference between the condenser and the evaporator. Danfoss manufactures multiple types of expansion valves to fulfill particular needs.

• The thermostatic expansion valve: is an automatic device that changes the orifice according to the temperature of the evaporator. It has a sensing bulb that monitors the temperature of the evaporator. Based on the temperature variation of the bulb, the valve modulates the refrigerant flow. This mechanism ensures that the refrigerant fully evaporates, preventing the overheating of the compressor.
• The Electronic Expansion Valve (EEV): An electronic expansion valve Danfoss, also called a stepper motor valve, uses a motor driven by pulses to change the refrigerant's orifice. This type of valve offers greater flexibility and precision than traditional thermostatic valves. An advantage of the electronic expansion valve is that it can be controlled to change the refrigeration system's energy efficiency. It can also be adjusted to fit varying working conditions. Danfoss EEVs are exact valves suited for precise refrigerant flow.
• The solenoid valve: This type of valve controls the refrigerant's on-off flow. When the solenoid valve is energized, the valve opens, allowing the flow of the refrigerant; when de-energized, it closes, stopping the flow. Solenoid valves are suitable for systems that need to control refrigerant flow by stopping or starting the flow of the refrigerant. Danfoss offers a wide range of solenoid valves for different applications with various features.
• The modulating valve: Unlike on-off solenoid valves that only allow for the refrigerant to flow in a binary state, modulating valves are designed to regulate the refrigerant flow continuously. They achieve this by changing the size of the refrigerant passages. Modulating valves allow the system to respond to different cooling demands smoothly.

Specifications and maintenance of Danfoss expansion valves

Specifications

• Capacity (kW): The capacity or power of Danfoss expansion valves ranges from 0.1 kW to 70.2 kW.
• Suction pressure: Low-pressure valves operate with suction pressures as low as 0.3 bar. Medium pressure is roughly between 2 and 8 bars. High-pressure (subcritical) valves can work up to 28.8 bars. Furthermore, Danfoss block valves operate at a pressure of 40.0 bars.
• Refrigerants: Danfoss expansion valves are suitable for several refrigerants, including hydrofluorocarbon (HFC) refrigerants such as R134A, R404A, and R23, Hydrofluorocarbons plus hydrocarbon blends HFC/HC R407 RC and R448A, Ammonia NH3, and carbon dioxide (CO2) within transcritical systems. Among them, HFCs are synthetic gases commonly used in refrigeration and air conditioning systems.
• Environmental ratings: Danfoss expansion valves have been developed to meet environmental regulations throughout the world. For instance, the pressure vessel standard, which is the international regulation for CO2, particularly in supercritical applications.

Maintenance

The maintenance of Danfoss expansion valves and other types of expansion valves mainly involves regular inspection and cleaning. During installation, people should ensure the correct fitting of the expansion valves. Therefore, there are no air leaks or ingress of contaminants. Another tip for valve maintenance is to keep the refrigerant charge at the required level. Proper system settings are also essential for maintaining valve operation. They ensure consistent performance and extend valve service life. In case of valve malfunction, early detection and timely repair can help avoid severe breakdowns and costly repairs.

Scenarios of Danfoss expansion valves

Both the Danfoss electronic expansion valve and the mechanical expansion valve are used in different scenarios in refrigerant-based machines.

• Commercial refrigeration systems

  Both the electronic and mechanical expansion valves control refrigerant flow in commercial refrigeration systems like display cases, cold rooms, and walk-in refrigerators. They regulate the evaporator's pressure and temperature, ensuring optimal refrigeration performance and consistent product quality.

• Heat pumps

  Danfoss electronic and ETVs play a major role in heat pump systems that transfer heat between different sources to provide heating or cooling. In heat pump mode, these valves regulate the refrigerant flow in evaporators and condensers, maximizing system efficiency and heat transfer.

• Industrial refrigeration

  The mechanical and electronic expansion valves are used in industrial refrigeration applications as process chillers, ammonia refrigeration systems, or hyperbaric cooling systems. These valves regulate the evaporator's refrigerant flow in large refrigeration setups, maintaining precise temperature control for industrial processes, storage, and equipment cooling.

• Air conditioning systems

  Both types of expansion valves are used in different air conditioning systems. Whether in a split, central, or Variable Airflow Volume (VAV) system, the electronic and mechanical expansion valves control the refrigerant flow into the evaporator. They monitor pressure and temperature for optimal evaporator usage and efficient air conditioning.

• Transportation refrigeration

  The electronic and ETVs also find their potency in transportation refrigeration systems, such as refrigerated trucks, containers, and trailers. Here, they regulate the evaporator's refrigerant flow, maintaining stable temperatures during transportation. This ensures the integrity and safety of temperature-sensitive goods in transit.

• Medical and laboratory refrigeration

  Whether It's the Electronic or Mechanical, the Danfoss expansion valve regulates temperature-sensitive applications in medical and laboratory refrigeration. They are responsible for precise temperature control in freezers, refrigerators, and cryogenic storage systems, ensuring reliable storage for valuable samples, drugs, and medical equipment.

How to Choose Danfoss Expansion Valves

Several factors must be considered when selecting the Danfoss refrigeration expansion valves for a particular application. To ensure proper functioning and efficient performance, they must be in line with the system's specifications.

• Compressive Function:

  Danfoss expansion refrigeration valves are available for both liquid refrigeration and gas pressure transfer. Liquid valves are used for refrigerant expansion from liquid to gas, while valve types are implemented for gas compression. The valve types should thus be chosen to fulfill the intended refrigerant function.

• Suction Side Service Pressure:

  This pressure is of utmost importance when determining the valve to be used. To maintain integrity and system safety, the Danfoss valve must be chosen to withstand the maximum estimated operating suction pressure.

• Temperature Control:

  Danfoss expansion valves work in different temperature ranges and applications. Identifying the temperature and refrigeration function are critical to selecting the right valve. For instance, in a supermarket refrigeration system, superheat control is important to prevent liquid refrigerants from entering the compressor. In this case, a thermostatic expansion valve would be suitable for application.

• Refrigerant Compatibility:

  Different types of valves are used for different refrigerants. Selecting a valve compatible with the system-recirculating refrigerant is important.

• Valve Sizing:

  The valve must be properly sized to optimize system efficiency as well as capacity. Factors such as the cooling capacity of the system, the temperature of the refrigerant, pressure and pipe dimensions must be considered to ensure that the valve selected performs with maximum efficiency.

Q&A

Q: How do Danfoss electronic expansion valves work?

A: The electronic expansion valves from Danfoss are used to control the refrigerant mass flow. They consequently control the evaporator superheating, which leads to the optimal use of the refrigerant's cooling capacity. The valve opens and closes in response to the signals coming from the temperature sensors.

Q: What are the factors to consider when buying Danfoss expansion valves?

A: The type of valve required for the specific application, the refrigerant used in the system, the capacity and pressure drop characteristics of the valve, and the system's temperature range.

Q: Are Danfoss valves TZR and TRP smart?

A: Yes. According to Danfoss, the TRP and TZR valves are intelligent electronic valves. They have an algorithm that improves the control of superheat. Moreover, they can be remotely diagnosed and configured.

Q: How long do expansion valves last?

A: An expansion valve was designed to last at least ten years under normal functioning. However, with appropriate maintenance practices, splendid valve longevity might be realized.

Q: Are faulty expansion valves repairable?

A: Unfortunately, faulty expansion valves cannot be repaired. Nevertheless, some manufacturers might offer valves Bluetooth that can be easily replaced with Danfoss valves by doing a quick disconnect plug.