Shell & Tube
Dryplus Evaporators
Dryplus shell-and-tube evaporators are designed for air conditioning, refrigeration and industrial process cooling/heating systems. They can be used with all HCFC and HFC refrigerants at operating temperatures ranging from -40°C to 90°C.
This range of dry-expansion evaporators consists of a wide selection of Dryplus-3 units, supplemented by special Dryplus-E models especially for large-scale air-conditioning and refrigeration installations.
Dryplus-3 evaporators are widely used as air-conditioning coolers, refrigeration brine coolers and process cooling evaporators, as well as being ideal for use in heat pump applications. These robust, reliable units are suitable for use with all HCFC and HFC refrigerants, and are currently available in 25 sizes, with one, two, three or four refrigerant circuits and cooling capacities of 18–1500 kW.
Dryplus-E units are specially designed to meet high Coefficient of Performance (COP) requirements in large industrial, commercial and HVAC installations – such as where year-round cooling is needed. They are optimized for high-efficiency duties using R134a as refrigerant, making it possible to comply with stringent environmental standards.
Dryplus-E evaporators are designed for exceptional efficiency even at partial loads. They are available with cooling capacities of up to 1420 kW and with one, two, three or four refrigerant circuits.
- How It Works
- EF
- Documentation
- EF How It Works
How It Works
This type of evaporator is basically a heat exchanger that uses the well-known shell-and-tube principle to achieve the desired effect. It consists of a pressure vessel (the shell) with a bundle of tubes inside it. The primary fluid (the refrigerant) flows through these tubes, while the secondary fluid (normally water or anti-freeze brine) flows over the tubes (through the shell) in order to bring about heat transfer from one fluid to the other. The tube bundle can consist of different types of tubes – copper inner-finned, stainless steel, carbon steel or copper-nickel
.
Dryplus units are dry-expansion evaporators, designed for use as one component in cooling systems that consist of a compressor, a condenser, an evaporator and an expansion valve. The two-phase refrigerant arrives at the evaporator from the expansion valve. It then flows inside the tubes and evaporates as it absorbs heat from the surrounding secondary fluid, which is cooled down by this heat loss.
The final part of the tube run is used to superheat the refrigerant. This is done because the refrigerant must always arrive at the compressor in vapour form in order to ensure the most efficient cooling possible. Specially designed baffles are used on the shell side in order to boost heat transfer efficiency still further.
EF
EF flooded evaporators Alfa Laval's series of flooded evaporators in the capacity range 200-1100 kW are designed to achieve the highest evaporation temperatures available in the industry in combination with oil-free compressors.
Heavy year-round air conditioning and process cooling increase demand for energy-efficient solutions at full and partial load.The aim of this evaporator concept is to maximize performance in terms of the power consumption of the compressor versus the achieved cooling capacity.
While a normal water-cooled chiller can ensure a coefficient of performance (COP) value around 5, EF flooded evaporators in combination with oil-free compressors can ensure COP values beyond 6 at full load. This efficient performance results in notably lower energy consumption in comparison with a traditional screw chiller. The EF series includes four evaporator models ranging from 225 kW (64 RT) to 1100 kW (313 RT) nominal cooling capacity in the single and double refrigerant circuit version.
This flooded evaporator series was specifically designed to operate with oil-free compressors and should not be used with other compressors.
EF flooded evaporator models are equipped with:
- Integrated separator, which permits no external vessel
- Optimal refrigerant distribution and tube geometry, preventing preferential flows
- Water-side low pressure drop design
- Global compactness, which reduces the footprint of the chiller and the refrigerant charge
The evaporator standard equipment includes compressor supports, welded feet and refrigerant sight glasses. Options like thermal insulation and liquid level management are available as non-standard alternatives (AISI316L for the water-side or Cu/Ni 90/10 for tubes).
EF How It works
Liquid refrigerant coming from the condenser enters the evaporator through a connection located underneath the shell. A distribution plate helps the refrigerant to flood the refrigerant circuit up to the highest row of tubes – normally placed at half of the shell height – avoiding preferential paths.
When the refrigerant makes contact with the tubes, it is boiling.
The evaporation process is completed as refrigerant vapour, including some liquid residual, ascends towards the compressor. The upper distribution plate blocks any remaining liquid droplets, thereby fully protecting the compressor.