One of the projects where a good cooperation has been reached between the customer who knows what he wants, designer and performer who can do it, is a new canning enterprise “Palirriya”.

The factory is a new investment of “Palirria Bulgaria” and as a result of experience gained they were able to prepare a precise specification. One of their requirements was the recuperation (recovery) of energy from the exhausted air.

The technological process is connected with intensive discharge of heat and moisture from certain work stations. Local suction helps the air exchange to be minimized, but still the ventilated air from the general circulation ventilation is more than 24 000 m³ / h.

The team of “Tangra” company constructed, produced and installed special energy recovering ventilation systems according to design of the engineer Ivan Nihtianov, manager of “INFA- TERM” Ltd. Kazanlak.

The nature of the technology imposed several problems:to be resolved:

• Agri – Food industry requires hygienic performance of air handling units;
• Intensive evaporation suggests sumptuous condensation in recuperators in winter mode;
• Condensed moisture is aggressive to standardly used materials.

The constructors of TANGRA company, taking into consideration the above mentioned features, have created a air handling units TANGRA AHU with high efficiency, allowing dismantling and cleaning of all elements.
The inner surfaces are made of non-corrosive steel (INOX) or polymer-coated, which allows precision cleaning. The two-stage filtering of the fresh airs provides the necessary clarity in the working area. Recuperators are made of extruded polypropylene blades resistant to destruction by exhausted air. A reserve set of Plate Heat Exchangers is provided in order to ensure cleaning with short interruption of ventilation supply.

Suction Centrifugal ventilators of air handling units are TANGRA TAT, which are resistant to corrosion because they are made of INOX 304 and INOX 316.

The system developed in such way has significant energy advantages:

• During the winter period, heat exchangers recover over 60 % of the energy of the exhausted air.
• Through automatic louver – boards natural cooling carry out during the transitional periods and non hot days (free cooling).
• There is a possibility to supply air conditioning in the summer.
• Inverter ventilators control is in full accordance with the requirements of technology and minimize energy costs.

Two-shift operation of the enterprise requires the installation to functioning sixteen hours per day. This influenced very favorably by reducing the payback period of capital investment on the basis of energy savings (about 150 MW hours per year).

The great number of studies have shown that a good microclimate is the basis for increased productivity and reduced risk of diseases. The energy saved is a prerequisite for less environmental pollution. “Palirria Bulgaria”. Nova Zagora is a good example of economically reasonable and socially responsible approach.