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The HVAC Components and Systems module of the Vital Signs Project was developed Walter Grondzik was Principal Investigator (and author) for the HVAC. Basic HVAC Scheme for Plants. .. Coordination of HVAC and Fire Detection and Alarm System E. Noise and Vibration. The sponsoring editor for this book was Linda Ludewig, the editing supervisor was David E. Wang published two air conditioning books and.
The water used in a chiller system is DM demineralized water. The only difference is that the capacity of the compressor is much more. This Chilled water which is at a temperature of 5.
Hence in a chiller system the refrigerant does not directly cool the warm area. The above diagram shows 3 chillers. The primary pumps are used to pump the water into the chillers.
Depending upon the amount of cooling required the compressors in each chiller is switched on or off.
The secondary pumps pump the cool water coming out of the chillers into the cooling coils of the various AHUs present in the building.
There are basically 2 types chilled water distribution. In case of constant flow a constant amount of chilled water is sent from the chillers into the cooling coils of the AHU.
Just remove the secondary pumps in the above sketch and you have a constant flow system. In case of variable flow system, apart from the primary pumps which circulate constant flow through the chiller, secondary pumps are present which vary amount of water flowing into the cooling coils of the AHUs.
The refrigerant in the chiller is either air-cooled or water-cooled. In case of water-cooled chillers the cooling tower is used to cool the water which cools the refrigerant. The cooling tower has fans. There is make-up water available to make up for any loss of water. A measure of the load condition is the difference between the supply and return header temperatures.
By measuring this difference, the load can be determined and energy saving means adopted, as will be illustrated below: If there is only one chiller, the microprocessor of the chiller will receive inputs of the supply and return header temperatures, apart from safety interlocks like water flow, refrigerant pressures etc and based on the difference, a decision on how many compressors can be switched on will be determined.
Example: Let us take the case of 2 chillers, each with its own microprocessor panel. This is because the microprocessor of chiller 1 will not know that there is another microprocessor panel of chiller 2 next to it.
Assuming no BMS or any other controls from Chiller manufacturer. Each chiller will switch off one compressor, as both the chillers have received same supply and return header temperature input. Please Note: Whether BMS is there or not, the chiller manufacturer will use temperature sensors in supply and return line of the chiller as inputs to the microprocessor. Also, one chilled water pump can also be shut down.
The same example can be extended to more number of chillers.
Please note: The decision to run the compressors of the chiller is taken by the micrprocessor panel of Chiller and not by BMS. BMS will only decide whether one or more chillers need to run. The operating of the compressors of the chiller, is referred to in HVAC industry, as loading and unloading of the chiller.
While switching off the chiller, The chiller is first switched off, then primary pumps and then the butterfly valve is closed. When again switching on the chiller the reverse sequence is followed. This air then passes across a cooling coil inside which cold water is running from the chiller, through the pumps.
Heat exchange occurs between the air and the chilled water in the cooling coil. The cooled air is then circulated into the supply air duct by means of a fan. Using ducts this cooled air is distributed to the various areas where this AHU is catering to.
A differential pressure switch connected across the filter is used to give a digital output when the filter is clogged. A differential pressure switch is used to monitor the functioning of the fan The AHU can also be operated on time schedule basis. For e. The AHU can be switched on from 9. The return air temperature of each AHU is used to monitor the opening and closing of the valve connected at the outlet of the chilled water line cooling coils.
If the return air temperature is high then the valve is opened wide. If the return air temperature is low, then the valve is closed allowing only little water flow. The air enters each room via a damper system. Each zone will have varying temperature and pressure requirements. This requirement is met by varying the closing and opening of the damper which in turn controls the amount of cool air flowing into the zone.
The VAVs are similar to the taps in each of the rooms. The water available in the overhead tank can be used in the rooms as per each rooms requirement by variably opening and closing the taps.
This temperature is monitored while using VAV. If the pressure is too high a Variable frequency drive is used to lower the speed of the AHU fan. To reduce RH we increase the cooling. Increased cooling leads to dehumidification.
Due to dehumidification the water content in the air reduces. Thus the RH of the room is reduced. After this process if the temperature of the room has to be increased a little then we can switch on the heater. Gllossary:: G ossary Humidity: It is the measure of moisture content in a substance.
Air always exists in the form of a mixture of dry air and water vapour. Relative Humidity: The ratio of the actual moisture content of air at a given condition to the moisture condition that would have been present at saturated conditions for the same temperature.
This book also has added information about microchannel heat exchangers written in a logical and progressive manner. You can also learn all about energy efficiency in detail, along with all the code alert features.
There are realistic illustrations along with the content as well, so you understand better 4. From the very basics of heating and cooling systems to the latest technologies being used in the HVAC field, you can get all your desired information in this book.
It also provides a review of the basics such as installing, wiring, and troubleshooting a system This book also lets you know which kind of system is best for what situation, according to the climate and the requirements Not only used for systems, this book is also a guide for the different fuel types and which fuel works best for which kind of system.
This book makes it very easy to install, maintain, and troubleshoot conversion units. It covers all the topics, situations, problems and their quick fixes which make it a total solution for the HVAC trainees and professionals. This HVAC training book is well known for its high quality of illustrations and the plethora of technical hints provided in the book. Along with these, this book also has tips from industry experts, review questions, and a whole lot more! The main content covered in this book include the introductions to heating, cooling, and air distribution systems, and the practices commonly used in piping, among more topics.
With all the information that is present about the HVAC industry, it is not possible for one person to learn and remember all of it. But if you stop learning, you resign your business to stay stagnant and stop growing. These books will you the tools needed for you to keep up with the pace of the industry.