(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

Turbomachinery Software for Education

Turbomachinery design has significantly evolved over the last two decades, as supporting education and training methods and techniques remains a challenge. Diversity of technologies covered in the varying courses and extensive use of software by industry designers makes the task of delivering the course curriculum that meets expectations of industry and students difficult. Many educational institutes and business use generic CAE tools for the purpose of learning turbomachinery through student projects. While generic tools have proven their value in research and design, the comprehensiveness of these tools to tackle real life turbomachinery situations is far from desired. The inexperience of fresh graduates from universities and colleges in their inability to perceive a 4D machinAxSTREAM EDUe (3D plus time), traditionally taught using a 2D blackboard, is evident. A student is not only required to have a very good understanding of underlying fundamentals, but is also required to address multitude of design, analysis and optimization problems within the limited time available for education. Coupling of theoretical and computer aided design knowledge to augment the capability of students to contribute to the industrial endeavor is necessary. Such a solution provides students with implicit understanding of the level of detail required by final designs, such as mean line design to the specification of a blade profile varying from hub to tip of a blade, and further complexities of iteration due to an aerodynamically correct blade profile being unsuitable because of stress levels or excitation frequencies and much more. AxSTREAM® EDU introduces multiple dimensions of design required by turbomachinery very early in the instruction process which, by using,  the students are able to develop insights that traditionally are difficult to attain in the same time frame. The use of AxSTREAM® EDU as a design software has been proven to multiply the skills of the students, enabling broad 3-D design considerations and visualization seldom possible otherwise.

AxSTREAM® EDU provides the user with the ability to design many different types of turbomachinery from scratch, such as axial turbines and compressors, radial compressors and turbines, axial fans, integrally geared compressors, mixed flow turbines and compressors and more. The moot question is how important is preliminary design? The efficiency gain possible to achieve in the preliminary design is of the order of 5-10 %, as compared to 0.5 % using 3D optimization (blade profiling, stress and CFD). One has an option of spending several weeks running  full 3D CFD calculations in generic software to try to optimize 0.5% of design, or spending much less time and resources using AxSTREAM® to figure out the best flow path design, followed by use integrated stress, CFD and rotor dynamic solvers!

Expander Configurations and Torsional Analysis

Lateral rotor-dynamic behavior is often discussed as one the critical aspects in determining the reliability and operability of rotating equipment. However, as multiple equipment are coupled together to form trains for centrifugal pumps, fans/blowers, compressors, steam or gas turbines and motors or generators, torsional behavior requires a thorough analysis. As per industry standards, torsional response is sought only for train units comprising of three or more coupled machines (excluding any gears).Blog 6

The configurations of the expanders used in the oil and gas industry makes it not only ideal but mandatory to perform train torsional analysis.  Expander trains are commonly used in CCU and FCU units and in the production of nitric acid. Serving the purpose of energy recovery, various arrangement for power recovery train are illustrated to the left:

As part of torsional analysis, the drive-train critical speeds (rotor lateral, system torsional, blading modes, and the like) need to be established to ensure they will not excite any critical speed of the machinery and the entire train is suitable for the rated speed and starting-speed hold-point requirements of the train. Finding frequency margins (torsional natural frequencies and torsional excitations) and if necessary undertaking stress analysis is mandated to demonstrate that resonances do not have  an adverse effect.RD

Such analysis requires modelling complexities of flexible supports, foundation, rotor seal interaction, instabilities etc. of the entire train and their interaction. SoftInWay’s CAE tool AxSTREAM® RotorDynamics is comprehensive, user friendly, and fully integrated with modules for flowpath and blade design making it unique to undertake train torsional analysis. Further information about the software is available by following the link

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/