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  1. [11]
    حسن هادي
    حسن هادي غير متواجد حالياً
    عضو متميز
    الصورة الرمزية حسن هادي


    تاريخ التسجيل: Nov 2006
    المشاركات: 1,338
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    Digital Control of a Mobile Air
    Conditioning System
    James Solberg
    ME 313 project
    Professor N. R. Miller
    5/12/98
    Abstract
    When automotive air conditioners are started up on a hot day, they are known to create
    whistling and hissing noises. These noises have resulted in customer complaints. It has
    been shown at the University of Illinois that the acoustic noise results from high speed,
    single phase vapor refrigerant flowing through the evaporator. It was then proposed to
    digitally control the A/C system to resolve this and other problems. It has also been
    proven at the University of Illinois that closing the expansion device can reduce the
    torque imposed on the compressor at startup. These two remedies along with a PID
    control algorithm where combined to formulate a control routine for a mobile air
    conditioning system. The algorithm is implemented by Dan Block’s DSP, and controls a
    mobile A/C system that uses an electric expansion valve (EEV) as its expansion device.
    Background
    Expansion Valves
    A schematic flow diagram showing the basic components of the vapor
    compression refrigeration system is shown in figure 1. Some typical temperatures for air
    conditioning applications are indicated. Refrigerant fluid circulates through the piping
    and equipment in the direction shown.

    Process 1 - 2.
    At point (1), the refrigerant is in the liquid state at a relatively high
    pressure and high temperature. It flows to (2) through a restriction, called the flow
    control device or expansion device. The refrigerant loses pressure going though the
    restriction. The pressure at (2) is so low that a small portion of the refrigerant flashes
    (vaporizes) into a gas. But in order to vaporize it must gain heat (which it takes from that
    portion of the refrigerant that did not vaporize), thus cooling the mixture and resulting in
    a low temperature at (2).
    Process 2 - 3.


    This is when the refrigerant passes through the evaporator. During
    this time, the refrigerant vaporizes, taking heat from the environment to do so. This is
    how an air conditioner cools air.
    Figure 1.


    The vapor compression refrigeration system.

    The expansion device can play a dual role. The most obvious purpose of an
    expansion device is to expand some of the liquid into gas by imposing a pressure drop.
    The expansion device can also be responsible for regulating the refrigerant flow
    according to the load.
    One of the two most common traditional methods of refrigerant control in
    automobiles is the orifice tube. The orifice tube is only able to exhibit a fixed restriction,
    and is not able to actively control the flow of refrigerant. The orifice tube has been
    traditionally used because of its low cost and high reliability due to the fact of no moving
    parts.
    The second of the two most common traditional methods of refrigerant control in
    automobiles is the thermal expansion valve. The thermal expansion valve is able to
    actively change the flow of refrigerant as needed by the system. A bulb filled with a fluid
    is strapped to the outlet of the evaporator, and thus, senses the temperature at this point.
    This bulb is connected to the valve by a tube in a manner so that the pressure of the fluid
    in the bulb tends to open the valve more, against a closing spring pressure. If the load in
    the system increases, then the refrigerant in the evaporator picks up more heat, and the
    temperature and pressure of the fluid in the bulb increases. This action is able to open the
    valve more to handle the increased load. Their disadvantage is they are less reliable than
    orifice tubes due to their moving parts and their relatively fragile capillary tubes.
    Electronic expansion valves have not been traditionally used for automotive
    applications due to the expense on such a system. An electronic expansion valve (EEV)
    system requires a computer to monitor the temperatures at the inlet and the outlet of the
    evaporator. From this feedback, the computer actively controls the valve setting. The
    versatility and efficiency of an EEV make it ideal for an automotive air conditioner, but,
    the cost is simply too great.
    Discussion
    DSP / AC Interfacing
    Dan Block’s DSP unit was chosen to initially control the mobile AC unit. The
    DSP is equipped with four digital to analog and to digital converters. Each has twelve
    bits of resolution and operates at a voltage range of -10 volts to +10 volts. There are also
    32 digital I/O lines, where 16 are input and 16 are output. These lines operate at +5 volts
    for logic high, and 0 volts for logic low.
    At the AC unit a thermocouple will be placed that the inlet of the evaporator and
    one will be placed at the outlet of the evaporator. An Omega linearized, isolated
    thermocouple input will be used to change -100


    oC to 400oC temperature to a 0 volt to 5
    volt signal. But, the greatest range that the thermocouples would experience is from
    -10


    oC to 30oC. This corresponds to a 0.9 volt to a 1.3 volt range. That is only 2% of the
    resolution of the DSP. It would be ideal to have -10


    oC correspond to -10 volts and 30oC
    correspond to a +10 volts.
    With constraints that -10


    oC correspond to -10 volts and 30oC correspond to a +10
    volts, the relationship between the input of the desired circuit to the output of the desired
    circuit is found to be:
    V


    out = 50*Vin- 55
    This would correspond to the following circuit
    Figure 2.


    Op-Amp circuit used to increase the resolution of the thermocouples.

    This circuit uses two inverting op-amps. The first op-amp has a gain of

    output would feed into a relay circuit where logic high (+5 volts) would engage the clutch
    and a low signal (0 volts) would disengage the clutch. The final interfacing between the
    A/C unit and the DSP is shown in figure 5.
    Figure 5.


    Interfacing diagram between the DSP and A/C unit.

    0.9V...1.3V
    -10V...+10V
    4mA…20mA
    -5V...+5V
    0V or +12V
    0V or +5V
    Control Algorithm
    The algorithm to control a mobile A/C system that is presented in this paper will
    address three issues:
    ·


    reduce compressor wear at startup
    ·


    reduce noise caused by high speed vapor through the evaporator
    الرابط ادناه للموضوع مع التقدير



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  2. [12]
    حسن هادي
    حسن هادي غير متواجد حالياً
    عضو متميز
    الصورة الرمزية حسن هادي


    تاريخ التسجيل: Nov 2006
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    :: Ducted Air Conditioning System

    Ducted systems also have 2 parts and interconnecting piping. They come in many sizes to suit most multi roomed areas. The fan coil unit is placed within your ceiling space, and this is piped to the condensing unit outside. Ductwork runs from the fan coil unit to outlets in each area. It is usually not possible to install a ducted system in the downstairs of a 2 story house without modifications. Ducted systems can be installed either for the whole of your home, or on a day/night system where air is diverted to either sleeping areas or living areas. This is usually not practical where young children sleep during the day. Most larger area ducted systems require the installation of 3 phase power.

    If you are thinking of installing a ducted air conditioning system in your house or your office, we are recommending either the Hitachi or the Daikin Inverter ducted air conditioners. Both manufacturers' iinverter technology provide the comfort of precise temperature control, reduce energy consumption and quiet indoor and outdoor units.

    To read the Hitachi DC Inverter Ducted Air Conditioners in PDF.
    To read the Daikin Inverter Ducted Air Conditioners in PDF.


    Home | Company | Ducted Aircon | Split System | Gallery | Contact

    Oregan Air Conditioning Pty Ltd© 2004 Designed by ejireh.net

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  3. [13]
    حسن هادي
    حسن هادي غير متواجد حالياً
    عضو متميز
    الصورة الرمزية حسن هادي


    تاريخ التسجيل: Nov 2006
    المشاركات: 1,338
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  4. [14]
    حسن هادي
    حسن هادي غير متواجد حالياً
    عضو متميز
    الصورة الرمزية حسن هادي


    تاريخ التسجيل: Nov 2006
    المشاركات: 1,338
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    سنقوم بالاضافة ان شاء الله

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  5. [15]
    حسن هادي
    حسن هادي غير متواجد حالياً
    عضو متميز
    الصورة الرمزية حسن هادي


    تاريخ التسجيل: Nov 2006
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    SMUD Home > Energy Education > CAT > HVAC summaries

    Heating, ventilation and air conditioning (HVAC) summaries


    It takes a lot of energy to heat and cool our homes and businesses. SMUD is well known for its innovation and pioneering spirit, particularly in the area of energyefficiency. Over the past three years, SMUD customers have installed numerous geothermal heat pumps, evaporative condensed air conditioners and indirect/direct evaporative cooling (IDEC) systems.

    The following summaries provide a brief explanation of each technology. To obtain a more complete report, download the PDF file. (Requires Adobe Acrobat Reader to view.)
    Note: SMUD does not endorse any specific product. These evaluations are provided as a public service.
    FREUS: Water-cooled air conditioning

    It's another sizzling summer day in Sacramento. Weather forecasters are predicting 100-plus temperatures all week long. The California Independent System Operator (Cal ISO) urges people across the state to conserve electricity.
    Although the energy crisis of 2001 might be over, the need for high efficiency air conditioning systems remains greater than ever. This technologoy brief focuses on a new residential air conditioning system known as the FREUS™. The FREUS is a water-cooled air conditioning system with great promise. Based on recent results, the FREUS may be nearly twice as energy efficient as conventional air-cooled systems. Learn more ...
    Download PDF
    Turbocor: Oil-free bearings, energy savings

    During the summer of 2004, the California Railroad Museum invested in a cutting-edge technology known as Turbocor™. The Turbocor is a centrifugal refrigeration compressor that uses oil-free, magnetic bearings. According to Danfoss Turbocor Compressors Inc., the manufacturer, Turbocor compressors are designed for 50 to 300-ton chiller and rooftop air conditioner applications. They offer significant energy savings and reduced maintenance costs. A full technology evaluation report is scheduled to be released in the fall of 2005. In the meantime, learn more about this exciting technology by reading the technology brief ...
    Download PDF
    The Coolerado Cooler: Innovative evaporative cooling system

    In 1998, Applied Behavior Consultants (ABC School) became one of the first commercial customers to install indirect-direct (two-stage) evaporative cooling (IDEC) systems. Unfortunately, these units have proven to be troublesome and a source of many comfort-related complaints. But ABC School recently agreed to test an an innovative evaporative cooling system known as the Coolerado Cooler. According to the manufacturer, Idalex, this compressor-less cooling system offers the same comfort levels as traditional air-conditioning systems at a fraction of the operating costs.
    Download PDF

    IDEC at ABC Inc.: Advantages of proper installation and maintenance

    Proper maintenance of heating, ventilation and air conditioning equipment is important. This is especially true for indirect or direct evaporative cooling (IDEC) systems. In addition, building owners and contractors often overlook other equally important steps: ensuring that designs are correct, inspecting contractors' installation work and commissioning the completed systems. Mistakes that are not found and corrected during design and installation can lead to poor system performance and make maintenance a nightmare.
    This report focuses on the IDEC system installations at Applied Behavior Consultants (ABC) Inc., which operates a school for children diagnosed with autism.
    Download PDF
    back to top

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  6. [16]
    حسن هادي
    حسن هادي غير متواجد حالياً
    عضو متميز
    الصورة الرمزية حسن هادي


    تاريخ التسجيل: Nov 2006
    المشاركات: 1,338
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    اذا لم تكن الروابط فعالة لديك استخدم الرابط التالي
    http://www.smud.org/education/cat/hvac.html

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  7. [17]
    حسن هادي
    حسن هادي غير متواجد حالياً
    عضو متميز
    الصورة الرمزية حسن هادي


    تاريخ التسجيل: Nov 2006
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    مع فائق الود والاحترام
    Natural, silent and without draft.
    An experience technique: the radiant/convection ceiling.
    The function of the KaRo Capillary Tube System was inspired by the Human Body. The water circulates inside a mat formed by capillary tubes. As the human body uses the blood circulation to regulate its temperature, the water of the KaRo Capillary Tubes System irrigates the building with temperature of:

    16˚C (60˚ F) and 40˚C (105˚ F).
    The KaRo Capillary Tube System refreshes room temperature by radiation and convection. A wall or ceiling temperature of 20˚C (68˚F) is enough to cool natural, silent and draft free way. The considerable rate of efficiency is obtained by the use of water as the cooling fluid, allowing very large energy savings!
    The provisions of the energy laws recently implemented throughout Europe offer a partial explanation for the current interest in the implementing of energy efficient measures and technologies in building construction in Europe.

    It is obvious that a similar result cannot be obtained in the US without serious re-examination of current building standards.

    So far, market control by the compressor-driven technology, preconceptions of the public, and the difficulty of overcoming traditional building practices have serious barriers to the adoption of radiant cooling in the United States.

    In Europe is perfect example of demonstrating the opportunities to alternative cooling technologies by government commitment to energy efficient.
    Why use Radiant Cooling?
    Air Conditioning Systems of Today

    Most air conditioning systems use the same principle of forced air. In forced air systems, warm room is circulated, chilled and blown back into the space. With the increased use of computers and other office technology, higher and higher heat loads need to be removed from these environments.

    To remove this additional heat, a higher volume of cooler air is blown into the working environment to maintain comfort, making draft-free cooling with chilled, primary air increasingly more difficult. An additional problem that came to light in the 1970’s and 1980’s is known as:
    “sick building syndrome”

    The standard forced air cooling system can carry the airborne spores to other locations in the building. Forced air systems can also expose occupants throughout a building to odors and cold viruses or contribute to "sick building problems".

    This high level of recirculation promotes the spread of potentially harmful and/or odor causing organisms.

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  8. [18]
    م. عبد المنعم
    م. عبد المنعم غير متواجد حالياً
    عضو شرف


    تاريخ التسجيل: Jan 2006
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    وسام الشكر

     وسام كبار الشخصيات

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    أخي الكريم حسن هادي ..
    ما شاء الله ..
    شكراً جزيلاً على موضوعك الرائع والقيم والضخم جداً ..
    جزاك الله خيراً ، وجعل عملك هذا في ميزان حسناتك ..
    دمت في رعاية الله وحفظه

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  9. [19]
    م. عبد المنعم
    م. عبد المنعم غير متواجد حالياً
    عضو شرف


    تاريخ التسجيل: Jan 2006
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    وسام الشكر

     وسام كبار الشخصيات

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    ونظراً لشمولية الموضوع ، فسيتم تثبيته بعض الوقت.. واسمح لي اخي الكريم بتعديل العنوان الى :
    تكييف الهواء ...

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  10. [20]
    حسن هادي
    حسن هادي غير متواجد حالياً
    عضو متميز
    الصورة الرمزية حسن هادي


    تاريخ التسجيل: Nov 2006
    المشاركات: 1,338
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    بارك الله فيك اخي الكريم **وبامكانك التعديل مع فائق الود والتقدير والاحترام

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