HITEMA MANAGEMENT WITH “INTEGRATED SOLUTIONS & ENERGY SAVING”

HITEMA is an international company in the treatment of compressed air, industrial refrigeration and air conditioning appliances technology.

ENERGY EFFICIENCY
The long standing know-how in the HVAC sector has allowed the company to make flexible products, and, underlines Hitema,  “to meet from time to time any type of request in a very short time”.

EER Comparison HITEMA Chillers

The attention to design and finish quality, combined with the use of selected components, has led to development  of a family of machines characterized by high EER and ESEER/IPLV values.  

FLEXIBILITY 
All condensate-air series, available in direct or indirect  free-cooling configuration, use semi-screw compressors partialised automatically in continuous, an economizer that increases the power cooling performance by 15%, condensing “EC-FANS” electronically switched that allow considerable acoustic and energy advantages, an electronic valve-rolling “EEV” and optimization of logic control through micro-processor.

This ensures energy savings up to 45% of electricity consumed power and precision on water outlet temperature that other traditional systems can not reach.
The constant pump flow rate to vary pressure provides interesting values of energy savings.

MANAGEMENT

The use of special algorithms can optimize free-cooling performance while reducing energy consumption and respecting the environment.

HITEMA solutions permit to manage, monitor and optimize air conditioning Systems for large technical environments.

Hydronic system and three-way valve.

The economizer is a device designed to improve both cooling capacity and efficiency of the system, by providing an additional sub-cooling, achieved with the addition of an intermediate plate heat exchanger, expansion valve and the cross flow refrigerant circuits.

Principle of operation

The compression in a screw compressor takes place by means of high speed rotors drawing  coolant into the rotor grooves of the opposing rotor teeth. They transport the volume, that is steadily reduced and so it is compressed, from suction pressure to condensing pressure.

The pressure at the additional middle connection (economised port) is similar to the intermediate pressure with a two-stage system (Fig.1)

As a result of these features, a screw compressor of this design can be combined with an additional sub-cooling circuit (ECO-VEE-SVE in Fig.1) for “two stage of compression”.

                                  Fig. 1)
These measures result in increased refrigeration capacity due to additional sub-cooled liquid entering the evaporator (Fig.1). The power consumption of the compressor increases only slightly when compared to the additional cooling performance.

System with economizer (sub-cooler)

The sub-cooling is achieved by injecting a part of the refrigerant from the condenser through an expansion device (VEE) in counter flow into the main sub-cooler flow, which then evaporates due to the absorption of heat. The superheated vapour is pulled into the compressor at the economizer connection and mixed with the vapour, which is already slightly compressed from the evaporator.

Increased power consumption, increased pressure and mass are only 25%, compared to the percentage of performance increasing. This is the reason of increment in the COP through the operation with economizer. 

                  Standard operation                                                    Economizer operation

Fig.2)  1 suction; 2 compression; 3 discharge; 4 under-compression; 5 rotor angle position

The higher the condenser temperature the greater is the cooling performance gain (Fig. 3).  If we consider an equal cooling between the standard solution and the economizer solution, then it can be possible to select a compressor smaller for the eco solution. Precise inverse proportion compared to full load performance.

With an economizer circuit the variation of performance in according with the variation of ambient temperature is flatter than a standard circuit. However with the decreasing of condensation temperature the surplus capacity due to economizer decreases too (Fig. 4).

Compressor can be selected with a less volumetric displacement about 17%. The improved efficiency of the compressor and the system too leads to a more favourable relationship between cooling performance and absorption compared to standard unit.

The refrigeration utilities have been tted, as mentioned, with an EEV (electronic expansion valve) and a TEV (thermostatic expansion valve), in alternating operation.                      
The EEVs have been installed for the purpose of ensuring the energy saving objectives, while also allowing the best possible operation of the refrigeration units and the installation as a whole. Proportional electronic expansion valves are the type that best  respond to the operating requirements: compared to pulsating valves, they in fact guarantee more stable operation of the refrigeration units and reduced pressure stress on the refrigerant lines. For every degree in less of the condensing temperature, you can obtain an energy saving of 2%. Compressor manufacturers put at disposal tables where it is showed the considerable COP increment of a refrigerating compressor when condensing temperature decreases (see the graphic).