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The DDC system is the "brain" of the HVAC system. It dictates the position of every damper and valve in a system. It determines which fans, pumps, and chiller run and at what speed or capacity. With this configurable intelligence in this "brain", we are moving to the concept of building automation. [2]
A block diagram of a PID controller in a feedback loop. r ( t ) is the desired process variable (PV) or setpoint (SP), and y ( t ) is the measured PV. The distinguishing feature of the PID controller is the ability to use the three control terms of proportional, integral and derivative influence on the controller output to apply accurate and ...
In the process, heat is absorbed from indoors and transferred outdoors, resulting in cooling of the building. In variable climates, the system may include a reversing valve that switches from heating in winter to cooling in summer. By reversing the flow of refrigerant, the heat pump refrigeration cycle is changed from cooling to heating or vice ...
Fig.1 Schematic diagram of a Stirling cooler. The system has one piston at ambient temperature T a and one piston at low temperature T L. The basic type of Stirling-type cooler is depicted in Fig.1. It consists of (from left to right): a piston; a compression space and heat exchanger (all at ambient temperature T a) a regenerator; a heat exchanger
The hard-wired nature of these components made it difficult for design engineers to alter the automation process. Changes would require rewiring and careful updating of the documentation. Troubleshooting was a tedious process. [4] When general-purpose computers became available, they were soon applied to control logic in industrial processes.
Thermoelectric cooling uses the Peltier effect to create a heat flux at the junction of two different types of materials. A Peltier cooler, heater, or thermoelectric heat pump is a solid-state active heat pump which transfers heat from one side of the device to the other, with consumption of electrical energy, depending on the direction of the current.
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A simple stylized diagram of the refrigeration cycle: 1) condensing coil, 2) expansion valve, 3) evaporator coil, 4) compressor. Cooling in traditional air conditioner systems is accomplished using the vapor-compression cycle, which uses a refrigerant's forced circulation and phase change between gas and liquid to transfer heat.