Greenhouse Ventilation Project

General exchange ventilation

General Information

General exchange ventilation is used to remove excess heat from the production zone, the sources of which are DNaT lamps of the plant irradiation system.

Calculation of required air exchange is performed according to the following initial data:

installed power of the irradiation unit of one vegetable compartment (6 × 6 m) is 18 kW;

air temperature taken from the upper area of the room is not more than 35 ° С;

air velocity 0.25-1.0 m/s;

temperature of supply air supplied to vegetable compartment for assimilation of excess heat not lower than 15 ° С.

The calculation was made for the most unfavorable conditions under which the greatest air exchange is required, such conditions are the following factors and assumptions:

heat flow power of DNaT lamp is equal to its rated electric power;

it is accepted that in the warm season there are no heat losses through the enclosing structures of the room;

it is accepted that there is no heat loss, at any time of the year, through the enclosing structures of compartments that do not have external walls;

calculation is carried out for the mode when all lamps of the irradiation system are turned on in three adjacent compartments 9 (1.2.3), 8 (1.2.3), etc., the power of the irradiation plant is 18 × 3 = 54 kW.

Design Solutions

The general ventilation system is divided into three independent sections of the same type .

Each section includes: ventilation chamber, air ducts of plenum and exhaust systems.

There are six ventilated compartments per section.

The principles and operation of the ventilation system are illustrated by one section venting vegetable compartments 8 (1), 8 (2), 8 (3), 9 (1), 9 (2), 9 (3).

Since the ventilation system is designed to assimilate excess heat coming from the lamps of the irradiation system, its operating mode is consistent with the schedule of the irradiation system, Figure 1.

The work schedule of the irradiation systems in the adjacent compartments 8 (1.2.3) and 9 (1.2.3) is shifted by 12 hours, i.e. they work in phase. Accordingly, ventilation schedules in adjacent compartments are also shifted by 12 hours. This allows you to install one pair of fans (for inflow and for exhaust) in six compartments. Air flows are controlled automatically by means of electrified gate valves (2) on sheet (13). This technical solution (both in the operation schedule of the irradiation systems and in the ventilation schedule) allows to reduce the total installed power of the fans by half and to level the daily schedule of the consumed electric power .

In vegetable compartments, air ducts of plenum and exhaust ventilation are located under the ceiling (elev. top of air ducts -0,500).

The exhaust system takes air from the upper area of the room, and the plenum system supplies air directly to the working area (to the internal space of the IAG unit).

Ventilation grids are cut into the exhaust air ducts, through which heated air is taken from the upper area of ​ ​ the room.

Flexible air ducts are cut into the plenum ducts, through which plenum air is supplied to the interior of the MUG installation.

Ventilation chamber

Fans of exhaust and plenum ventilation systems and electric gate valves are installed in the ventilation chamber. The air supplied to the greenhouse shall be at least 15 ° C. To maintain the required temperature, warm air from the exhaust ventilation system is partially mixed into the air taken from the environment. For this purpose, between the air ducts of exhaust and plenum ventilation, an electric gate valve controlled from the automation system is installed. That is, the general ventilation system operates with partial recirculation. The degree of recirculation increases proportionally as the outside air temperature decreases .

This solution avoids the installation of supply air electric heaters and consequently significantly reduces the power consumption of the ventilation system.

A ventilation grate with an adjustable gap is also cut into the exhaust air duct to discharge part of the heated air into the rooms of the ventilation chamber in the winter.

List of regulatory documents

SNiP 2.04.0591 * Heating, ventilation and

conditioning.

Manual 1.91 to SNiP 2.04.0591 * Calculation and distribution of supply

air.