For the start of the 2015/2016 ski season, the renovation of Hotel "Rila" in Borovets resort was completed.
The common areas have been renovated: restaurants, lobbies, panoramic bars, a nightclub, gaming and conference halls, a SPA center, and an indoor swimming pool. The facade has been completely updated with efficient thermal insulation and decorative balcony railings.
The main contractor for the construction and installation works was "Kordeel-Bulgaria" EAD, while the company “TANGRA” was selected to supply the HVAC equipment.
The hotel’s ventilation and air-conditioning systems were upgraded in line with the hotel’s new design, as well as criteria for high efficiency and low energy consumption.
“TANGRA – AV” Ltd. was tasked with manufacturing, installing, and commissioning the main HVAC equipment in the hotel’s machine rooms.
The supplied air handling units have capacities ranging from 1,000 to 18,000 m³/h, with a total treated air volume of 200,000 m³/h. A major challenge was the dismantling of the old units and the installation of the new ones. The existing machine rooms had limited access, requiring the delivered equipment to be fully disassembled, brought in, and then reassembled on site.
Within the machine rooms of the newly installed systems, measures were taken to reduce noise transmission to adjacent rooms and the surrounding environment. TANGRA AHU air handling units were successfully integrated into the newly installed BMS system, which is responsible for controlling, monitoring, and optimizing the processes of the ventilation and air-conditioning equipment.
For the needs of the three restaurants, lobby bar, nightclub, and service areas, TANGRA AHU ROT air handling units with capacities ranging from 5,000 to 15,000 m³/h were supplied. They are equipped with rotary regenerative heat exchangers with an efficiency of 72–80%. Fresh air reheating is performed using a water-to-air heat exchanger. Built-in recirculation and inverter-controlled fans allow regulation of the fresh air supply according to occupancy. The air handling units can also operate in a “free cooling” mode, using outdoor air as a cooling medium.
The kitchen ventilation systems have been completely renewed. The new air handling units are TANGRA AHU REC type, with capacities ranging from 5,000 to 18,500 m³/h. These units operate entirely on fresh air without recirculation. The TANGRA REC plate-type air-to-air heat exchangers prevent odor transfer between the two air streams. Water-to-air heat exchangers are used for reheating the fresh air. The heat exchange sections in the air handling units are designed for convenient disassembly, allowing easy cleaning of the recuperators.
The conference center and casino are air-conditioned with central air handling units TANGRA AHU DEX, featuring two-stage heat recovery, with processed air capacities of 6,000 m³/h and 10,000 m³/h. The first stage of energy saving is achieved by the so-called “passive” element – a rotary regenerative heat exchanger with efficiency up to 78%. This stage preconditions the fresh air for the “active” element in the recovery process – the heat pump module. The heating capacity is supplied using the exhaust air.
The efficiency of the heat pump module alone, at the given fresh air parameters, is:
- temperature -8°C, COP=4.24, heating mode ;
- temperature +30°C, ЕЕR=3.35, cooling mode;
The efficiency of the unit (double recovery without electric power for the fans) at:
- temperature -8°C, COP=9.8, heating mode;
- temperature +30°C, ЕЕR=4.86, cooling mode;
This can be most commonly translated as: 9.8 kW of thermal energy obtained for 1 kW of electrical energy consumed.
The ventilation and air-conditioning unit for the pool dehumidification system has also been renovated.
The delivered unit is a TANGRA AHU DEX M with double heat recovery and a capacity of 15,000 m³/h. During winter, dehumidification is achieved through a plate-type air-to-air heat exchanger with an efficiency of up to 66%, a heat pump unit, and a peak water heat exchanger. At an outside temperature of -8°C and 90% humidity, the full heating capacity is 197 kW, and the dehumidification capacity reaches up to 120 kg/h.
In summer, moisture removal is carried out by the heat pump unit. Fresh air is cooled and reheated sequentially, with reheating achieved via an additional condenser connected to the heat pump. This approach saves energy and eliminates the need for the water-based heating section. The dehumidification capacity reaches up to 80 kg/h.
Two autonomous dehumidifiers, type TANGRA ACU DEX, are installed in the suspended ceiling of the pool, operating on full air recirculation. These compact climate units feature an integrated evaporator and compressor–condenser assembly. The dehumidification capacity is 5.8 kg/h with an air flow rate of 2,500 m³/h.
For the air conditioning of the multifunctional hall, a zoned VAV system has been installed, consisting of six units for both recirculated and fresh air. The system allows maintaining different temperatures and smoothly adjusting the fresh air flow depending on the number of people in each zone. The treated air is supplied from the ceiling of the hall through TANGRA SRD-type diffusers. By adjusting the direction of the airflow, high throw distance is achieved in heating mode, and even distribution in cooling mode. Air return is realized through the suspended ceiling of the rooms. Silent floor convectors installed near the windows further enhance the comfort of the hall.
For the pre-treatment of fresh air in both modes, a central air handling unit of the TANGRA AHU DEX type with double recovery is used. High efficiency is achieved through the sequential treatment of fresh air with a rotary heat exchanger and the integrated heat pump unit. The fresh air capacity ranges from 6,000 to 18,000 m³/h, with a heating/cooling capacity of:
- a full heating capacity of 215 kW at a temperature of -8 °C;
- a full cooling capacity of 110 kW at a temperature of +30 °C;
- at an outside temperature of -24 °C, the required heating capacity is supplemented with a water-to-air plate heat exchanger;
The silent operation of the installations is a key factor for comfort in such facilities. Using specialized software from TANGRA, the silencer sections for the air-handling units were properly sized, manufactured, and installed. This ensures noise levels remain below regulatory limits, both within the hotel and in the surrounding environment.
The successfully completed project is yet another milestone in TANGRA’s long-standing experience in implementing air-conditioning and ventilation equipment. It demonstrates the high quality of the company’s products and their ability to meet any client requirement.
