AIR-COOLED CHILLERS
Air-cooled chillers powered by screw compressors exceeding the efficiency demands of today and offering reliable cooling, a wide operating map, and sustainable refrigerant options
Applications: Air conditioning • Process cooling • Commercial
Lightstream Screw II is a follow-up to the successful line of Kaltra’s screw chillers known for exceptional reliability and a wide operational map that makes these chillers perfectly suitable for a variety of running conditions. Together with improved energy efficiency at peak and partial loads and high environmental sustainability, these Ecodesign-compliant air-cooled chillers are easily configurable for the stringent requirements of today’s demands.
The high level of flexibility inherent in Lightstream Screw II design and the long and varied list of optionals offer a means to create complete cooling plants based on a single unit or multiple machines running coordinately.
Many of applications depend on critical cooling processes where reliability is a key priority, and that is where one of Lightstream Screw II’s major values.
OPTIMIZED FOR HIGH SEASONAL ENERGY EFFICIENCY
The compressors used for Lightstream Screw II chillers are succeeding generation compact screw compressors of two-shaft rotary displacement configuration, designed for use in chillers with improved seasonal efficiency and featuring mechanical capacity regulation via solenoid valves, economizer operation in full-load, and adapted Vᵢ-compensation for part-load operation. This enables accurate capacity match and optimized efficiency in a wide operating range.
Compressors are designed for use with both traditional and lower GWP refrigerants and optimized for the Ecodesign Directive ambient temperature profile for liquid chillers.
Low vibration levels, service-friendly design, and advanced oil management system with integrated oil separator guarantee a long chiller lifespan without performance degradation.
Significant refrigerant charge reduction by up to 50% achieved for Lightstream Screw II with the use of microchannel condenser coils with multiport tubes having orifices of sub-millimeter diameter, which dramatically decrease the internal volume of the coil.
Brazed joints provide low contact resistance and, in combination with large heat transfer surfaces, enable high heat transfer characteristics for Lightstream Screw II chillers.
Improved corrosion resistance is another advantage inherent in microchannel coil technology. Heat exchanger components are made of long-life aluminum alloys with a zinc arc spray finish. Additional corrosion protection required for installations in highly polluted zones or coastal applications can be achieved with epoxy electrophoretic or trivalent chromium process coatings available optionally.
Condenser fans with impeller geometry enhanced by computational fluid dynamic analysis and controlled by state-of-the-art control software ensure very quiet and efficient operation while drawing less energy – also due to the lowest pressure resistance created by microchannel condenser coils.
Electronically commutated motors with continuous monitoring, less stressed windings and bearings contribute to higher reliability and longer lifespan, while quieter operation results in increased acoustical comfort. Especially at partial loads, Lightstream Screw II chillers equipped with EC-driven fans represent a significant opportunity to save on operating costs.
Lightstream Screw II chillers can be equipped with either shell-and-tube or low-charge falling film evaporators with improved heat transfer characteristics.
SHELL-AND-TUBE EVAPORATOR
Shell-and-tube heat exchangers provide improved thermal performance thanks to optimized flow paths, inner-grooved tubes, and baffles that increase fluid velocity. The net results are closer approach temperature and accurate control of return water temperature – major factors directly related to operating costs and overall chiller efficiency. Evaporators feature overpressure and freezing protection and high-grade insulation.
FALLING FILM EVAPORATOR
Falling film evaporators featuring refrigerant distribution through a spray arrangement above the tube bundle, thus creating a thin film of liquid around the tubes. This type of evaporator permits operation with close approach temperatures between the refrigerant and process fluid and provides high heat transfer coefficients. Falling film evaporators require less refrigerant charge compared to shell-and-tube evaporator designs – without compromising the system’s capacity and energy efficiency.
The control solution for chillers with screw compressors has been developed around a programmable controller based on a high-speed microprocessor and powerful yet flexible software adopting stepwise capacity control. The software dynamically controls operating limits by continuous reading suction pressure, discharge pressure, and other operating parameters to maintain the chiller’s working point, ensuring maximum chiller protection, reliability, and efficiency.
Giving complete control over the system for the plant operator, the chiller software manages and optimizes the chiller’s performance according to cooling demand and ambient conditions, generates safety and security alarms, supports interlinked, coordinated operation of multiple units, provides diagnostics and run statistics, and allow easy integration with any BMS protocols.
LOWER GWP REFRIGERANTS
Refrigerants significantly influence the chiller performance and environmental sustainability of the cooling solution. For Lightstream Screw II chillers, we offer non-ozone-depleting R134a refrigerant, as well as low-GWP refrigerants R1234ze, R450a, and R513a, which make these chillers a true leader in environmental safety - without compromising the performance.
Refrigerant charging amounts are kept to a minimum thanks to microchannel condenser coils with 60% lower internal volume and optimized evaporators.
Various customer needs can be fulfilled by configuring standard systems with optional components. Three grades of soundproofing available to meet noise requirements, low- or high-ambient kits adapting the system to environmental conditions, as well as enlarged condensers for improved performance. Optionals also include:
Free cooling version provides low energy cooling and enables significant savings at low-ambient conditions. In mild temperature conditions, when the ambient temperature drops below the return water temperature, the free cooling system operates in parallel with mechanical cooling, maximizing energy savings. Through the use of microchannel cooling coils, the air temperature at which the free cooling system provides 100% cooling demand is higher by 3°C to 5°C compared to heat exchangers of other types. The flow through the cooling coils is controlled through a 3-way mixing valve managed by the chiller software.
|
Capacity [kW] |
250 … 1850 |
|---|---|
|
Design |
AIR-COOLED |
|
Compressors |
SCREW |
|
Refrigerant |
R134A/R450A/R513A/R1234ZE |
|
Energy efficiency (EER) |
UP TO 3.56 |
|
Seasonal efficiency (ESEER) |
UP TO 4.89 |
|
Fan motors |
EC/AC |
|
Condensers |
MCHE |
|
Evaporators |
SHELL-AND-TUBE/FALLING FILM |
|
Evaporation control |
EEV |
|
Refrigeration circuits |
SINGLE/MULTIPLE |
|
Warranty |
3 YEARS |
