The dry coolers are units consisting mainly of a finned air/water heat exchanger that allows to cool a flow of water, which flows through the pipes of the exchange coil, using the ambient air. It is a very simple system, easy to install.
The only energy used by these systems is that used by the fans that move the air that flows through the pipes of the heat exchange coil. Over the years, this type of unit has been improved from an energy point of view, thanks to the use of new technologies such as EC fans. This type of electronically controlled fans allows to reduce the electrical absorption of the fans through the use of a system that allows to modulate the rotation speed according to external conditions.
When the external temperature or the thermal demand are reduced compared to the design conditions, the modulation allows to reduce the absorbed energy thereby increasing the economic savings for the company and, at the same time, reducing the noise level. The unit with EC fans tends to have higher investment costs than traditional technologies and that is why a cost/benefit analysis is essential to evaluate its convenience and payback times.
Dry coolers are used in closed circuit systems. This allows to minimize the contamination of the water with the outside air (as happens for example in evaporative towers) and allows to avoid waste of water (the fluid in the circuit is always the same).
The operating limits of the unit essentially depend on the outside air temperature. Generally, the fluid always comes out hotter than the external temperature by a value close to 5-10 °C, to allow the heat exchange between the two fluids. Lower values may require an increase in the size of the unit with a consequent increase in investment costs. This makes it clear how the yield of the unit is closely linked to seasonality: high values of the air temperature reduce the heat exchange and therefore the yield of the unit; low values of the temperature increase the exchange and therefore the yield of the unit.
It is important to pay attention to the conditions of the outside air in the coldest periods of the year.
Air temperature values below 0 °C increase the risk of freezing of the fluid inside the pipes, with consequent system breakage. For this reason, in these conditions the use of solutions with a low freezing point, such as water/glycol mixtures, is preferred. Alternatively, in the event that the system is not in operation in these periods, complete drainage of the fluid is necessary.
The dry cooler solution can be adapted for different fluids (water, water/glycol, diathermic oils) and for different environmental conditions. There is also the possibility of adapting the materials of the exchangers to the environment in which the unit will be installed. This is the case of installation in corrosive environments or with highly aggressive atmospheres for the traditional materials with which the dry coolers are built (copper pipes and aluminum fins). In this regard, it is useful to provide information on the installation site during the sizing phase.
It is also possible to request different geometric configurations that best suit the place where the unit will be positioned.
The dry coolers are units consisting mainly of a finned air/water heat exchanger that allows to cool a flow of water, which flows through the pipes of the exchange coil, using the ambient air. It is a very simple system, easy to install.
The only energy used by these systems is that used by the fans that move the air that flows through the pipes of the heat exchange coil. Over the years, this type of unit has been improved from an energy point of view, thanks to the use of new technologies such as EC fans. This type of electronically controlled fans allows to reduce the electrical absorption of the fans through the use of a system that allows to modulate the rotation speed according to external conditions. When the external temperature or the thermal demand are reduced compared to the design conditions, the modulation allows to reduce the absorbed energy thereby increasing the economic savings for the company and, at the same time, reducing the noise level. The unit with EC fans tends to have higher investment costs than traditional technologies and that is why a cost/benefit analysis is essential to evaluate its convenience and payback times.
Dry coolers are used in closed circuit systems. This allows to minimize the contamination of the water with the outside air (as happens for example in evaporative towers) and allows to avoid waste of water (the fluid in the circuit is always the same).
The operating limits of the unit essentially depend on the outside air temperature. Generally, the fluid always comes out hotter than the external temperature by a value close to 5-10 °C, to allow the heat exchange between the two fluids. Lower values may require an increase in the size of the unit with a consequent increase in investment costs. This makes it clear how the yield of the unit is closely linked to seasonality: high values of the air temperature reduce the heat exchange and therefore the yield of the unit; low values of the temperature increase the exchange and therefore the yield of the unit.
It is important to pay attention to the conditions of the outside air in the coldest periods of the year. Air temperature values below 0 °C increase the risk of freezing of the fluid inside the pipes, with consequent system breakage. For this reason, in these conditions the use of solutions with a low freezing point, such as water/glycol mixtures, is preferred. Alternatively, in the event that the system is not in operation in these periods, complete drainage of the fluid is necessary.
The dry cooler solution can be adapted for different fluids (water, water/glycol, diathermic oils) and for different environmental conditions. There is also the possibility of adapting the materials of the exchangers to the environment in which the unit will be installed. This is the case of installation in corrosive environments or with highly aggressive atmospheres for the traditional materials with which the dry coolers are built (copper pipes and aluminum fins). In this regard, it is useful to provide information on the installation site during the sizing phase.
It is also possible to request different geometric configurations that best suit the place where the unit will be positioned.
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