What Is a Chilled Beam?

The cold beam system is driven by the temperature difference between the water inside the coil and the air outside the tube to form an air circulation. The system achieves the purpose of air conditioning through convection and radiation between the indoor air and the coil.

Cold beam

Right!

The cold beam system is between the water inside the coil and the air outside the tube.

The active cold beam system is an air conditioning system that integrates cooling, heating and ventilation functions. It can provide a good indoor climate and control of individual areas. The primary air is mainly used to eliminate the indoor wet load, and it can also supply heat, cold and ensure the fresh air; the end heat exchange coil is used to handle the indoor hot / cold load. In the summer, the treated main airflow enters the cold beam and then enters the lower end of the cold beam through the nozzle. According to the Venturi effect, when high-speed air flows through the barrier, the air pressure near the port above the lee side of the barrier is relatively low, which causes adsorption. The room air at the lower end of the cold beam flows upward due to this effect and passes through The heat exchanger was cooled. The cooled air is mixed with the main airflow, the temperature is lower than the room temperature, and then enters the room to cool the air there. After this same cycle, the heat of the room is taken away by the cooling coils, thereby achieving the cooling effect. Hot water flows in the heat exchanger in winter, so the cold beam plays a heating role.
Condensate pans are usually installed under the coils of active cold beams. Once the cold water temperature is lower than the dew point temperature, dew condensation occurs, and the condensate can be collected by the condensate pan.
The passive cold beam system is an air conditioning system that integrates cooling and heat exchange functions. This system must be operated in conjunction with an independent primary air system. The primary air is mainly used to eliminate indoor wet load and ensure fresh air. The end of the passive cold beam relies on the principle of complete natural convection for cooling and heat exchange. The hot air flow rises and the cold air flow sinks, which will cause a circulating air flow in the room. The cold beam system combines the advantages of comfort, low noise, energy saving and low maintenance.

The air flowing from the cold beam will form two opposite airflows, which flow along the ceiling to both sides of the cold beam. This airflow forms a very good airflow organization in the room. The air flow along the ceiling creates the Coanda effect, which flows along the ceiling, and then slowly flows to the cold place. Due to the strong blowing without a fan, the user will feel very comfortable in the cold area; the air circulation formed by the cold beam is very uniform, giving the impression that it is in nature, which will increase the user's warmth and natural sense. Thereby improving the quality of life. Among them, the left side of the window in summer is affected by solar radiation and conduction heat, which makes the area naturally convection obvious, the air forms a large buoyancy, and it is easy to cause the supply air flow to be blown away from the glass outer window. This phenomenon is called blocking effect. , Resulting in poor local high temperature air distribution in the peripheral area. Therefore, the jet direction of the air should avoid the glass vertical.

(1) Wide capacity range, cold beam has high cooling and heating capacity.
(2) Easy installation, cold beam equipment can be easily integrated into the ceiling of various materials.
(3) Low noise, the nozzle with special treatment keeps the minimum noise while producing the maximum effect.
(4) No motor, save energy.
(5) Adaptability. Cold beam equipment can have different lengths and widths, which makes cold beams suitable for almost all suspended ceilings.

The initial investment is high, and condensed water will be generated when it is out of control. Therefore, how to effectively detect, avoid and control the condensation problem of the ceiling in the cooling state and how to deal with the condensed water once it is out of control are important issues affecting the development of cold beams. In addition, the application of cold beam air supply system will be limited by the following factors:
(1) When the airtightness of the envelope structure is poor, it will cause outdoor humid and hot air to penetrate, and contact with cold beams may cause condensation.
(2) Because the coils of the cold beam system are dry coils, they are not suitable for restaurants, gyms, swimming pools and other places where the indoor latent heat load is relatively large and there is a risk of condensation.
(3) The cold beam system is not suitable for places with high requirements on indoor ventilation times, such as industrial clean rooms or biological clean rooms of all levels.
(4) The cold beam system is not suitable for places with many indoor pollution sources such as chemical laboratories and exhaust cabinets.

1. Cold beam 1. Air treatment of cold beam

The primary air of the cold beam system is usually fresh air, and part of the return air can be used. The use of new return air mixing can save energy, but it is necessary to set the return air, so the air duct system will be more complicated. Air treatment process for the new return air mix of the cold beam system:
First, the outdoor fresh air is mixed with the indoor return air to obtain the state point Q, which is cooled to the dew point K of the machine from the mixing point Q; the air supply state point O is obtained from the temperature difference of the supply air along the indoor iso-humidity line, and the state points K and O are mixed to point C. The indoor air heat-moisture ratio reaches the indoor state point N.
Design steps for cold beams:

(1) Pass the indoor state point N on the enthalpy-humidity diagram, and then determine the air supply state point O from the air supply temperature difference.
(2) From the mixing ratio of the fresh return air, the point Q after mixing is obtained. QK is the processing process after the fresh return air is mixed. The wet load that the mixed wind must bear is: The air quality is obtained from the above formula, and the K point is the intersection point with U = 95%.
(3) Induction ratio: From this point, point C can be determined.
(4) The indoor residual heat Q is caused by and burdened separately. One of the air handling boxes handles the cold capacity; the cold inner coil handles the cold capacity.
An important parameter that determines the performance of an active cold beam system is the induction ratio (n), which is defined as the ratio of the secondary air flow to the primary air flow. The magnitude of the induction ratio reflects the cooling of the cold beam (or Heating) capacity. The larger the induction ratio, the greater its cooling (heating) capacity. In other words, in order to obtain a certain cooling (or heating) capacity, the amount of primary air required for induction is larger than that of a large cold beam. But the magnitude of the induction ratio also reflects the magnitude of the noise and the pressure loss of the primary air. The greater the cold beam's induction ratio, the greater the primary air pressure loss.

2. Cold beam 2. Control of cold beam water distribution system

The water distribution system is an important part of the cold beam system. Taking the active cold beam as an example, because the temperature of the chilled water of the air-conditioning box and the cold water of the cold beam are different, there is a big difference, so two sets of chiller are needed, namely a high-temperature chiller and a low-temperature chiller. The supply and return water temperatures of the two chiller units are: 7 / 12 , 16 / 19 . According to the control diagram of the cold beam water distribution system in the literature, it is found that if the low temperature water unit fails, it can only use the high temperature water unit to replace the low temperature water unit, and it loses its own role, that is, only the cooling water to the air conditioning box. No cooling water to the cold beam. After improvement, no matter which chiller fails, the stable operation of the system can be guaranteed.
Under normal circumstances, both units are running normally, valves 1, 2, 3, and 4 are closed, and circulating pumps A and B are opened. When the low-temperature chiller fails, the high-temperature chiller is used to drive the entire system. 2, 3 and 4 are opened, valve 1 is closed, and the circulation pumps A and C are opened; when the high-temperature chiller fails, the low-temperature chiller is used to drive the entire system. Valves 1 and 4 are opened, valves 2 and 3 are closed and the cycle is started. Pumps A and B are turned on.
Under normal circumstances, the high-temperature water pump sends 16 high-temperature frozen water into the cold beam. After absorbing heat in the room, the return water temperature rises and enters the water collector through the return pipe. The cold beam water supply pipe is equipped with an electric regulating valve. The opening degree of the electric regulating valve is controlled by the room temperature controller. When the room temperature is higher than the set value, the valve opening degree is increased; when the room temperature is lower than the set value, the valve is reduced. Opening degree to keep the temperature in the room constant. The induced fresh air is sent into the room through the cold beam after being processed by the air processor. Since the number of indoor office workers does not change much, the required fresh air volume is basically constant, so the blower operates at a fixed frequency.

3. Cold beam 3. Cold beam prevention condensation control system

In order to ensure that no condensation occurs on the cold beam, the relative humidity of the indoor air is generally controlled below 50%. At the same time, a condensation prevention temperature sensor must be installed to measure the temperature of the cooling water entering the cold beam. The temperature controller measures the indoor temperature. The air temperature and humidity are then calculated as the dew point temperature. The deviation is compared with that in the cold ceiling controller. When the deviation e is a negative deviation, the electric valve is closed to induce the air to stop cooling, the indoor temperature rises, and the cold beam coil No condensation will occur everywhere.