In this article we briefly explain the main calculation modes of Coils, and the point of view with which our program analyzes the various modes.
After starting Coils, on the left, we will find the following calculation modes:
As we know, Coils calculates in Heating, Cooling, Condensing, Direct Expansion, Steam, Pump Evaporator, and in addition, from the professional version onwards, Partial Condensing.
Let’s start with Heating: coils considers the air point of view, so it is the air that is heating up. On the air side, the fluid heats up. On the tubes side, the fluid cools down. No phase change in this case.
Cooling: here too, Coils considers cooling from an air point of view, so it is the air that cools down. On the air side, we have the fluid that cools down, and on the tube side, the fluid heats up. No phase change. Coils manages both dry cooling and dehumidification.
Condensing: In this case, there is condensing, so there is a phase change, from gas to liquid! On the air side the fluid heats up, on the tube side it changes phase, and let’s remember, phase changes always take place at constant pressure and temperature. Coils calculates two types of condensing:
- when the air temperature at the compressor side outlet is lower than the saturation temperature
- when the air temperature is higher than the condensing temperature, for example the gas coming out of the compressor is at 80°C and the condensing temperature is at 50°C, and then the air comes out at 55°C.
Direct expansion: By direct expansion we mean the evaporator. There is an evaporation, so the fluid goes from liquid to gaseous: in other words, a phase change, and as already indicated, the phase changes occur at constant pressure and temperature. On the air side, the fluid is cooling down. On the side of the tubes, there is a phase change.
Steam: in Steam mode, condensation occurs. On the air side, the fluid heats up. On the tubes side, steam enters the pipes and liquid flows out. There is once again a phase change.
Pump evaporator: in the pump evaporator, the air-side fluid cools down, while the pipes-side fluid changes from liquid to gas. The pump evaporator, as the name suggests, uses a pump to recirculate the fluid. Typical examples are carbon dioxide or ammonia plants, where this type of evaporator is widely used.
Partial condensing: The last mode, available from the professional version, divides the exchanger into three parts, and calculates desuperheating, condensing and subcooling, then calculating the surface.
From the Enterprise version onwards, a small box with three additional calculation modes is added.
Smooth tube: Smooth tube means smooth externally, without fins. This type of coil is used in cooling towers or refrigerated counters.
External tube mixture: this mode considers other gas mixtures on the air side, outside of the tubes, and even flooded batteries, very similar to the concept of shell and tube heat exchanger!
Recuperators N-M: used in heat recovery, and to recover thermal energy from the exhaust gases of an industrial process, often positioned in the supply and return side of air handling units, they are also called closed circuit recovery units, or run-around coils system, or Bfly recuperators.
This is a brief summary of the modalities calculated by Coils. But our program does not stop there, there is much more to discover. Contact us at email@example.com for more information, a demonstration and other information and technical sheets of our product!