(English) Introduction to HVAC Systems

During the past week we’ve talked about challenges, improvements and development of HVAC technology. But taking a step back, what is a HVAC system? Heating, ventilation, air conditioning systems and refrigeration (or known as HVAC&R) is a technology developed to manipulate environment temperature and air quality. The applications of such technology are based on the principles of thermodynamics, fluid mechanics and heat transfer.

HVAC Intro
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Commonly HVAC systems are grouped into four main systems starting with the heating and air conditioning split system, which is the most ordinary implementation of residential applications encompassing both inside and outside installations. The application, which can be controlled with a central thermostat, consists of air conditioning system which cools the refrigerant to drop the temperature, and heating system which involves gas furnaces. Ducts used to circulate the adjusted air from both heating and conditioning, with the help of evaporator/fan coils – a terminal unit which is used to provide heating or cooling to the targeted space.

A split system is known for its simplicity, efficiency and low cost.  That being said, the second type (hybrid heat split system) is actually found to benefit over the first one from an energy efficiency standpoint since the application utilizes heat pump systems. With the incorporation of heat pumps, the system is able to pump cooled or heated refrigerant to make both system able to be controlled through electric power. The heat pump is used to move energy using outside surrounding air as an air source for heating and heat sink for refrigeration/conditioning systems.

A duct free split system would benefit the most to be installed at locales where conventional ducts cannot fit or are not directly connected to central control thermostats. No ductwork would be needed in the system, thus enabling flexibility of delivering air directly to the targeted zones. Since the technology allows you to directly zone the cooled air, using ductless technology could improve efficiency, lower operation cost and reduce carbon footprints.

The last system to note is the packaged heating and air conditioning system – which is normally the system that is installed at locales where there is not enough spaces available for  the components of the split system. A package unit has a heating and cooling system combined into one unit,  making it easier to access for maintenance as well as to be conservative on installation space.

References:

http://www.command-air.com/blog/benefits-of-a-packaged-hvac-system/

https://www.servicechampions.net/what-are-the-different-types-of-hvac-systems/

http://www.mitsubishicomfort.com/articles/ductless/5-advantages-of-ductless-cooling-and-heating-systems

Air Conditioning in Automotive

Car AC
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While the term of air conditioning in relation to automotive might instantly correlate to a system which provides passenger with a comfortable air temperature/environment, HVAC systems also are used for heating and cooling of batteries in such application as well as cooling of the vehicle fuel systems. Thermal management for automotive application isn’t easy though. Many factors have to be accounted for in order to build a dependable cooling system.

While talking about HVAC concerns and challenges which arise in automotive application, the biggest inconvenience commonly comes down to the lack of cold air produces. Mobile refrigeration/air conditioning systems come with quite a few concerns from two sides: the refrigeration side, where it removes heat and injects cold air, and from the electrical side which provides control. From the system, the most common challenges are found in moisture –which would fail the cooling system if present in the air, soiled condenser which would block air flow, and various other mechanical complications which might occurs.

While diagnosing an air conditioning issue, especially if environment temperature seems higher than it should be, there are few conditions that can be looked into including freon leak, failed blower, damaged or failed motor, damaged condenser to the most common problem usually arises from the compressor. Compressor, compressor clutch switch, fuses, wires, fan belt and seal are at the top of the list to be check for functional adequacy. Consequently, with many concerns arising from the compressor side of the system, a good and reliable compressor design must be implemented to avoid unwanted challenges during operation. Design your automotive turbomachinery with SoftInWay! Ask us about the projects that we’ve done in this field and how our turbomachinery development code will be helpful for your automotive and HVAC design, analysis and optimization activities.

References:

http://www.doityourself.com/stry/5-common-car-air-conditioning-system-problems

http://www.aa1car.com/library/ac98.htm 

http://www.agcoauto.com/content/news/p2_articleid/256

http://blog.firestonecompleteautocare.com/ 

为潮湿气候而设计的暖通空调

Blog for HVAC system

潮湿的气候通常伴随着湿度标准的挑战。当暖通空调(加热、通风和空调调节)系统不能保持适当的湿度条件/进行湿度控制时,就会造成建筑物的损坏和缺陷。

潮湿的气候特指当环境中的空气的平均每月潜热负荷(从空气中除去水分所需的能量)与夏季冷却空气所需的平均每月能量相同或更高的情况。高潜热负荷的空气容易使水分进入建筑材料并积累在其中。

湿度的保持控制不是一件容易的事情。 暖通空调装置必须能够使用干燥过的空气来支持整个建筑物适当的加压系统。为了提供最恰当的除湿干燥程度,暖通空调系统必须能够对流过冷却盘管的空气进行除湿(这意味着必须精确选择冷却盘管的尺寸以满足外部空气和回流空气的负载)。但这不仅仅是暖通空调系统得以实现的唯一指标。系统还必须具有足够的运行时间来将室内空气中的水分去除。毕竟,在潮湿的环境中,仅有温度控制是不够的, 湿度控制总是次要考虑因素(尽管在保证给用户提供舒适问题的前提下,温度控制也是必须满足的)。

在天气潮湿的地理区域,如东南部,公共住房一般采用冷冻水的直接蒸发作为冷却系统。这需要室外冷凝器装置将室内的热量与室外空气进行交换。

Reference:

http://www.greenseal.org/Portals/0/Documents/IG/PHA%20Manuals/Chapter2_Southeast_Green_Building_OM_Manual_PHA.pdf
http://www.tandfonline.com/doi/abs/10.1080/01998590309509232?journalCode=uene20