دورة التحليل والتصميم

 

دورة منظومة إدارة المباني

 

 دورة Autodesk Revit Architecture

 

 

التبريد والتكييف من الالف الي الياء

بسم الله الرحمن الرحيم وحدة مركزية.........central station الأحمال الجزئية......partial load إشعاع حرارى......ratiant heat السعة الحرارية......heat copacity مكان صناعى........industrial الحرارة المحسوسة...sensible

صفحة 6 من 83 الأولىالأولى ... 23456789101656 ... الأخيرةالأخيرة
النتائج 51 إلى 60 من 825
  1. [51]
    عضو فعال جداً
    الصورة الرمزية hishont2


    تاريخ التسجيل: Feb 2006
    المشاركات: 184
    Thumbs Up
    Received: 27
    Given: 0

    بعض المصطلحات باللغة الأنجليزية

    بسم الله الرحمن الرحيم
    وحدة مركزية.........central station
    الأحمال الجزئية......partial load
    إشعاع حرارى......ratiant heat
    السعة الحرارية......heat copacity
    مكان صناعى........industrial
    الحرارة المحسوسة...sensible heat
    الحرارة الكامنة......latent heat
    هواء الأمداد........supply air
    الهواء الخارجى.....outside air
    الهواء الخارج....leaving air
    الهواء العادم......exhaust air
    الماء المثلج........chilled water
    بوابات التوجية.....face dempers
    مبادل حرارى......heat exchanger
    الترطيب........hum idification
    رشاشات المياة........auxilary sprays
    مراوح طاردة مركزية.....centr ifugal fans
    ريش عدلة...................straight blade
    ريش مقوسة.................curved blade
    فى أتجاة الدوران............foruard surved
    فى عكس الدوران.........backword curved
    الهواء الأبتدائى .............primary air
    الهواء الثانوى..............secondary air
    موزع هواء................air diffuser
    غازات خانقة...........ckoke damb
    صمام فاصل.............disconnecct valve
    صمام توزيع...........distributer valve
    الأتزان الحرارى.........heat balancec
    الأحتكاك.........friction
    ثلآجة...........fridge
    موصل.........conductor
    الضاغط........compressor
    ضغط..........pressure
    المجففات.........dryers
    مضاد........inclined
    السرعة......velocity
    بخار.........steam
    خليط.......mixture
    مجارى....ducts
    فعال ومؤثر....effective
    تصميم تصنيف.....design
    درجة حرارة........temperature
    معامل.........factor

    0 Not allowed!


    مشرف تبريد وتكييف

  2. [52]
    عضو فعال جداً
    الصورة الرمزية hishont2


    تاريخ التسجيل: Feb 2006
    المشاركات: 184
    Thumbs Up
    Received: 27
    Given: 0
    بسم الله الرحمن الرحيم
    وحدة مركزية.........central station
    الأحمال الجزئية......partial load
    إشعاع حرارى......ratiant heat
    السعة الحرارية......heat copacity
    مكان صناعى........industrial
    الحرارة المحسوسة...sensible heat
    الحرارة الكامنة......latent heat
    هواء الأمداد........supply air
    الهواء الخارجى.....outside air
    الهواء الخارج....leaving air
    الهواء العادم......exhaust air
    الماء المثلج........chilled water
    بوابات التوجية.....face dempers
    مبادل حرارى......heat exchanger
    الترطيب........hum idification
    رشاشات المياة........auxilary sprays
    مراوح طاردة مركزية.....centr ifugal fans
    ريش عدلة...................straight blade
    ريش مقوسة.................curved blade
    فى أتجاة الدوران............foruard surved
    فى عكس الدوران.........backword curved
    الهواء الأبتدائى .............primary air
    الهواء الثانوى..............secondary air
    موزع هواء................air diffuser
    غازات خانقة...........ckoke damb
    صمام فاصل.............disconnecct valve
    صمام توزيع...........distributer valve
    الأتزان الحرارى.........heat balancec
    الأحتكاك.........friction
    ثلآجة...........fridge
    موصل.........conductor
    الضاغط........compressor
    ضغط..........pressure
    المجففات.........dryers
    مضاد........inclined
    السرعة......velocity
    بخار.........steam
    خليط.......mixture
    مجارى....ducts
    فعال ومؤثر....effective
    تصميم تصنيف.....design
    درجة حرارة........temperature
    معامل.........factor

    0 Not allowed!


    مشرف تبريد وتكييف

  3. [53]
    جديد


    تاريخ التسجيل: Jun 2006
    المشاركات: 3
    Thumbs Up
    Received: 0
    Given: 0

    احتساب عدد و حجم وحدات التكييف للغرف

    اشكركم جميعا على المعلومات المفيدة الواردة في هذا المنتدى. لدي مشاركة تتعلق بكيفية احتساب حجم و عدد وحدات التبريد اللازمة لكل غرفة في المنزل أثناء التخطيط للتصميم و هي حسابات تقريبية بسيطة تجدونها في الملف المرفق
    يمكنكم زيارة الرابط أدناه للمزيد من الإيضاحات.
    و شكراً
    http://www.openxtra.co.uk/articles/c...-heat-load.php
    اخوكم م. علاء اسماعيل من اليمن

    0 Not allowed!


    الملفات المرفقة

  4. [54]
    عضو شرف


    تاريخ التسجيل: Aug 2005
    المشاركات: 1,306

    وسام الشكر

     وسام كبار الشخصيات

    Thumbs Up
    Received: 25
    Given: 0

    Thumbs up خالص الشكر والتقدير

    السلام عليكم ورحمة الله وبركاته

    أود ان اتقدم بخالص الشكر والتقدير لجميع الاخوات والاخوة المشاركين في القسم عامة .. وموضوع التبريد والتكييف من الالف الي الياء خاصة علي جهودهم معنا ..

    وبالطبع خالص الشكر والتقدير لجميع المشاركات في جميع الموضوعات المطروحة بالقسم المتميز بأعضاءه ..

    و أعتذر عن عدم تواصلي معكم نظرا" لبعض الظروف ..

    والله الموفق ،،، والله المستعان ،،،

    0 Not allowed!


    إن تصدق الله .. يصدقك


    من ترك شيئاً لله .. عوضه الله خيراً منه



  5. [55]
    عضو


    تاريخ التسجيل: Jul 2006
    المشاركات: 15
    Thumbs Up
    Received: 0
    Given: 0

    من مجال دراستى

    يمكن تقسيم هذا المجال الى ثلاثة اقسام :
    1>تكييف هواء
    2>تبريد
    3> تجميد
    التكيف الهواء:هو ظبط درجة حرارة الهواء ودرجة رطوبتة وتنقيتة وتوزيعة وتحريكة ليفى باحتياجات الحيز المكيف
    وانا عممت شوية فى التعريف لانى مقدرش اقول درجة حرارة معينةاو درجة رطوبة معينة لان تكييف الهواء مش بس للاشخاص فى تكيف هواء لمصانع وغرف تعقيم وغرف حضانا وصوامع فى جميع المجالات الصناعية والزراعية الطبية والمعامل الكمياءية واكتر من كدة
    وممكن تقسيم تكيف الهواء الى الاتى
    1} تكيف هواء صحراوى
    2} تكيف هواء شباك
    3} تكيف هواء منفصل: حاءطى _ ارضى سقفى _ كونسيلد .مختفى . _ فرى استاند _
    4} تكييف هواء مركزى مصغر
    5}تكيف مركزى تشلر
    6} تكيف هواء مركزى موزود بواحدات مناولة هواء
    7}وحدات تسخين الهواء
    8} وحدات تبريد الهواءد
    9} وحدات ترطيب الهواء
    عفوا ساقوم بالتكملة فى وقت لاحق

    0 Not allowed!



  6. [56]
    جديد


    تاريخ التسجيل: Sep 2006
    المشاركات: 7
    Thumbs Up
    Received: 0
    Given: 0
    السلام عليكم ورحمه الله وبركاته
    عزيزي القارء من خلال دراستي اطرح موضوع يمكن الاستفاده منه
    يحدث عاده في المكيف عمليات تحول وقصد بذالك تحول السائل الى بخار او متجمد ولهاذه العمليات اسماء علميه مثل
    تسمى عمليه تحول الغاز الى سائل عمليه تكثف وعمليه تحول الصلب الى سائل عمليه انصهار
    ومن سائل الى صلب عمليه تجمد ومن سائل الى غاز عمليه تبخر ومن صلب الى غاز عمليه تسامي مثال على تحول الصلب الى غاز مثل البخور ولكم الشكر على قرائتكم .

    0 Not allowed!



  7. [57]
    عضو


    تاريخ التسجيل: Jul 2006
    المشاركات: 15
    Thumbs Up
    Received: 0
    Given: 0
    اخى العزيز الفرق بين وحدة الباكدج والتشيلر كلاتى

    package unit:

    وهى عبار عن وحدة تكييف ولكن قدرتها علية نسبيا ومكونى من جزاين كاى جهاز تكييف سبليت عادىولكن القدرة علية والمكونات هى
    الوحدة الخارجية } وهى وحدة تكثيف مكونة من الضاغط والمكسف واداة الانتشار والمراوح وغيرها من متممات الداءرة

    الوحدة الداخلية } وهى عبارة عن ملم المبخر والمراوح خاصتة وممران للهواء الهواء المبرد والذ يدخل الغرفة هواء منقى ذات درجة حرارة وضغط ونسبة رطوبة مناسبة لتفى باحتياجات الحيز المكيف مع العلم بان الغرفة مزودة بجريلة توزيع ومدخل للهواء الفرش ومخرج للهواء الراجع وقدراتها تبدا من 25 طن تبريد وحتى 80طن تبريد


    chiller unit:

    اما الاتشيلر هذانوع اخر من المكيفات حيث ان طريقة التبريد داخل الغرفة مختلفة فهو عبارةو عن ماكينة تكييف عملاقة وتوضع فى مكان منعزل خاص بها ولكن المبخر او الوحد التى توفى الغرفة هنا لم توضع وايضا يتم تغيير نوعها حخيث ان المبخر يكون من النوع ذو اغلاف والملف او الانابيب والملف وفى هذة الحالة يتم تبريد المياه ويكون محلول ميا ممكن ان يكون محلول براين وناتى بالمياه الباردة تقوم مضخة بسحبها ودفعها الى العرف المراد تبريدها حيث يوجد فى كل غرفة ملف تبريد يمر بة مياى باردة مزود بفلاتر ومراوح خاصتةواكيد يوجد خط مياه ليغذى جميع الغرف وايضا خط للمياة الراجع وقدراتة تكون اعلى من الاجهزة الباكدج

    0 Not allowed!



  8. [58]
    جديد


    تاريخ التسجيل: Nov 2006
    المشاركات: 8
    Thumbs Up
    Received: 0
    Given: 0
    مبدأ عمل مكيف السيارة


    يتألف مكيف السيارة من الأجزاء التالية :
    الضاغط وهو نصف مفتوح _ المكثف _ المجفف والخزان وعين الرؤية _ صمام التمدد _ المبخر _ صمام ضبط المبخر _ وأيضا يزيد في ذلك صمامات عدم الرجوع
    مبدأ سير وسيط التبريد
    _ الضاغط وهو نصف مفتوح يركب جانب موتور السيارة ويوجد عليه صمامات سحب وضغط والذي يأخذ عمله من السيور المركب على موتور السيارة وبواسطة التحريط المغناطيسي والذي يضغط وسيط التبريد عبر صمام الضغط إلى المكثف
    _ المكثف : يركب أمام السيارة والذي بدوره يحول وسيط التبريد من الحالة الغازية الى الحالة السائلة وثم يذهب وسيط التبريد إلى المجفف
    _ المجفف : وهو قطعة واحدة مع الخزان وعين الرؤية والذي يركب على جانب السيارة أي جانب الضاغط والذي بدوره ينقي وسيط التبريد من الرطوبة ويمر بعين الرؤية الذي يكشف عمل وسيط التبر وبعد ذلك إلى الخزان والذي يمنع مرور وسيط التبريد ( الحالة الغازية ) من دخول صمام التمدد
    _ صمام التمدد : وبدوره ينظم دخول وسيط التبريد إلى المبخر وهو يركب داخل كبين السيارة / تحت التابلو/
    _ المبخر : والذي بدوره يحول وسيط التبريد من الحالة السائلة ألي الحالة الغازية وبدرجة حرارة منخفضة ويركب المبخر في الكبين أيضاُ تحت التابلو ومن ثم يذهب وسيط التبريد إلى صمام الضبط ويركب خارج الكبين / جانب الضاغط على خط السحب والذي بدوره يضبط المبخر من التجميد ومن ثم يعود إلى الضاغط .
    ــــــــــــــــــــــــــــــــــــــــــــــــــ ــــــــــــــــــــــــــــــــــــــــــــــــــ ـــــــــــــــــــــــــــــــــــ

    0 Not allowed!



  9. [59]
    عضو متميز
    الصورة الرمزية حسن هادي


    تاريخ التسجيل: Nov 2006
    المشاركات: 1,333
    Thumbs Up
    Received: 7
    Given: 0
    Supermarket
    refrigeration system
    RESULT 272
    Centre for the Analysis and Dissemination of Demonstrated Energy Technologies
    Highlights
    • Reduction in CFCs
    • COP improved by
    26%
    • Investment payback
    period 3.5 years
    Terminator technology improves
    supermarket refrigeration system
    e n e r g y e ff i c i e n c y
    IEA
    OECD
    CA 96.508/2A.F09
    Summary
    Since Terminators, or
    secondary internal
    condensers, were installed
    in the cooling system at
    IGA-Marché André
    Bilodeau supermarket in
    Montreal, Canada,
    optimisation of the system
    operating parameters has
    been possible, leading to
    a 43.5% reduction in
    refrigerant gas and
    savings in electricity
    consumption of 21.3%.
    The modifications to the
    system resulted in an
    increased condensation
    capacity. As a result, the
    coefficient of performance
    (COP) was improved by
    26%.
    The Phenex Terminator
    increases the efficiency of
    refrigeration systems. It
    can also be applied in
    other air conditioning,
    cooling and industrial
    refrigeration sectors.
    Terminator installed in a freezer at IGA.
    Aim of the Project
    The objectives of this project
    were to demonstrate the
    operating performance and
    increased condensation
    capacity of the Phenex
    Terminator technology on an
    existing refrigeration system.
    Since early 1994, tests have
    been carried out to evaluate
    actual performance in practice.
    The improvement in overall
    productivity of refrigeration
    systems and the beneficial
    effects to the environment are
    the two main characteristics of
    this technology. The Terminator
    makes it possible to:
    • reduce the amount of CFC
    required for effective
    operation of refrigeration
    systems;
    • reduce the power demand;
    • lower operating costs;
    • extend the life of the
    equipment.
    The Principle
    In a refrigeration cycle, gas is
    compressed and then condensed
    at a higher temperature,
    forming a liquid. In the
    process, heat is removed from
    the object to be cooled. The
    pressure is relieved and, as a
    consequence, reduces causing
    the liquid to evaporate back
    into a gas. Operating parameters
    are chosen with a
    relatively wide safety margin to
    prevent the liquid entering the
    compressor and causing
    damage. Installing the Terminator,
    which acts as a secondary
    internal condenser, is a way of
    reducing these parameter
    settings so that the refrigeration
    cycle is optimised. Figure 1
    shows the main operating
    principles of the Terminator.
    The Situation
    Installation of the Terminator
    required replacing the check
    valve which prevents the liquid
    from flowing down from the
    condenser. In addition, control
    of the condenser fans was
    needed to cycle the fans,
    according to demand and the
    outside temperature. With the
    Terminator installed, the overtemperature
    settings of the
    pressure-release valves had to
    be read and adjusted to enable
    the evaporator performance to
    be improved under the new
    operating conditions. In practice,
    one pressure-release valve
    had to be replaced as it could
    not sustain the prescribed overtemperature.
    In addition, a
    malfunctioning oil pressure
    gauge was changed. The
    operating parameters were
    continually reset to obtain the
    desired level of cooling, about
    32
    °C on average, in the
    freezers.

    Table 1: Operating parameters before and after Terminator installation - 2221 system alone.
    Without With Reduction with
    Terminator Terminator Terminator
    Average current (A) 18.58 15.72 15.4%
    Average power used (kW) 4.62 4.02 13.0%
    Average electrical power consumption (kWh) 110.83 96.43 13.0%
    Refrigerant charge (kg) 30 23 23.1%
    Figure 1: Secondary internal condenser (Terminator).
    Saturated
    mixture from
    condenser
    Saturated
    liquid
    towards
    evaporator
    4
    Saturated liquid
    towards
    thermostatic valve
    2
    3
    1
    Gauge
    Thermostatic valve
    Saturated
    liquid towards
    the secondary
    internal
    condenser
    Terminator
    The first system, No. 2221,
    consisted of a 5.6 kW (7.5 HP)
    compressor, developing a
    capacity of 15.5 kW (53,000
    BTU/hour), and two 3.66 m
    (12-foot) freezers. The second
    system, No. 2222, used a
    2.25 kW (3.0 HP) compressor
    developing 7.8 kW (26,600
    BTU/hour), and an additional
    3.66 m (12-foot) freezer. Both
    systems operated on CFC R-12
    supplied by an exterior
    condenser.
    Thermco Canada carried out
    two case studies, firstly by
    installing the Terminator on the
    existing 2221 system alone,
    and secondly with the addition
    of the freezer from the 2222
    system. Tables 1 and 2 show
    changes to the operating
    parameters, after optimisation,
    for the two cases.
    The addition of the extra
    freezer increased the load on
    the 2221 system somewhat,
    although it remained under its
    limit of 5.6 kW (7.5 HP). In
    theory, a power of 5.28 kW
    corresponds to a 7.08 HP
    compressor, which means that,
    without the technology, the
    compressor would have had an
    induced overload of more than
    5.6 kW (7.5 HP).
    As the motor is now operating
    near its maximum load, it is
    more efficient. Prior to
    installation of the system, the
    COP for the refrigeration
    Without With Reduction with
    Terminator Terminator Terminator
    Average current (A) 26.58 20.37 21.3%
    Average power used (kW) 6.71 5.28 21.3%
    Average electrical power consumption (kWh) 161.24 126.71 21.4%
    Refrigerant charge (kg) 52 29 43.5%
    Table 2: Operating parameters before and after Terminator installation - 2221 system + 2222 system
    cabinet.
    system was 4.47. After installation,
    however, this
    increased to 5.62, an increase
    of 26%, which means improved
    efficiency and a higher performance
    system. Consequently,
    installation of the
    Phenex Terminator technology
    increases the condensation
    capacity of the system to a
    significant degree and in a
    beneficial way.
    Additionally, the 2.25 kW
    (3.0 HP) compressor of the
    2222 system could be shut
    down, resulting in savings in
    energy and maintenance.
    Figure 2 shows a diagram of
    the liquid line system with the
    Terminator installed.
    Originally marketed as the
    Thermco Terminater,
    Phenex Refrigeration Inc.
    aquired all rights to the product
    which now carries the name
    Phenex Terminator
    The Company
    Founded in 1926, IGA (International
    Grocers Alliance) is
    the world’s largest supermarket
    network. Through its global
    alliance of 3,600 supermarkets,
    IGA has an annual turnover of
    CAD 16.8 billion. IGA
    currently has operations in
    Figure 2: Liquid line system diagram.
    5
    2
    1
    3
    6
    High pressured
    saturated gas/
    liquid mixture 40
    °C
    Gauge
    Heat gain
    Gas/liquid
    evaporator
    4.5
    °C
    Evaporator
    Secondairy internal
    condenser (terminator)
    TXV
    100%
    liquid
    32-35
    °C
    Compressor
    Superheated
    gas 13
    °C
    Heat loss
    Condenser
    69
    °C
    High pressured
    gas at elevated
    temperature

    IEA
    The IEA was established in 1974 within the
    framework of the OECD to implement an
    International Energy Programme. A basic
    aim of the IEA is to foster co-operation
    among the 23 IEA Participating Countries to
    increase energy security through energy
    conservation, development of alternative
    energy sources, new energy technology, and
    research and development (R&D).
    This is achieved, in part, through a
    programme of energy technology and R&D
    collaboration currently within the framework
    of 39 Implementing Agreements, containing
    a total of over 70 separate collaboration
    projects.
    Swentiboldstraat 21,
    6137 AE Sittard,
    P.O. Box 17, 6130 AA Sittard,
    The Netherlands,
    Telephone: +31-46-420-2224,
    Telefax: +31-46-451-0389,
    E-mail: nlnovcce*ibmmail.com
    Internet: http://www.caddet-ee.org
    * IEA: International Energy Agency
    OECD: Organisation for Economic
    Co-operation and Development
    The Scheme
    CADDET functions as the IEA Centre for
    Analysis and Dissemination of Demonstrated
    Energy Technologies. Currently, the Energy
    Efficiency programme is active in 15
    member countries.
    This project can now be repeated in
    CADDET Energy Efficiency member
    countries. Parties interested in adopting this
    process can contact their National Team or
    CADDET Energy Efficiency.
    Demonstrations are a vital link between
    R&D or pilot studies and the end-use market.
    Projects are published as a CADDET Energy
    Efficiency 'Demo' or 'Result' respectively, for
    on-going and finalised projects.
    Please write to the address below if you require more information.
    March 1997
    Neither CADDET Energy Efficiency, nor
    any person acting on their behalf:
    (a) makes any warranty or representation,
    express or implied, with respect to the
    information contained in this
    brochure; or
    (b) assumes any liabilities with respect to
    the use of this information.
    It is permissible to make a copy of this
    publication as long as the source is
    acknowledged.
    This brochure is printed on 100% chlorine-free bleached paper
    *
    e n e r g y e ff i c i e n c y
    IEA
    OECD
    Host Company
    IGA-Marché André
    Bilodeau
    5000 Beaubien EST
    Montreal, Quebec
    H1T 1V5 Canada
    Tel.: +1-514-259-8281
    Contact: Mr A. Bilodeau
    Monitoring Agent/
    Main Contractor
    Multi Energies Inc.
    1, Place du Commerce
    (Room 500)
    Ile des Soeurs, Quebec
    H3E 1A2 Canada
    Tel.: +1-514-769-6048
    Fax: +1-514-766-4236
    Contact: Mr R. Ross/Mr MA.
    Lamarre
    Element Savings
    (CAD per year)
    Refrigerant 7,500
    Equipment 6,000
    Energy 1,200
    Total 14,700
    Table 3: Savings generated by
    the installation of the
    Terminator.
    50 states and 21 other
    countries, commonwealths and
    territories. IGA Inc. is owned
    by 19 marketing and
    distribution companies.
    The André Bilodeau IGA
    supermarket has a sales area of
    13,500 m
    2 and employs approximately
    50 people.

    Economics
    The investment required to
    install the Terminator
    technology at IGA was
    CAD 49,000 for 37 units. The
    savings generated by the installation
    are about CAD 22,000
    for the first year and approximately
    CAD 15,000 for each
    year thereafter. The savings
    from this project will make the
    investment profitable in 3.5
    years.

    0 Not allowed!



  10. [60]
    عضو متميز
    الصورة الرمزية حسن هادي


    تاريخ التسجيل: Nov 2006
    المشاركات: 1,333
    Thumbs Up
    Received: 7
    Given: 0

    Refrigeration effect

    BSME-ASME International Conference on Thermal Engineering
    31 December 2001 – 2 January 2002, Dhaka
    Optimal Performance of an Endo-reversible Solar Driven
    Sorption Refrigeration System
    K.C.A. Alam and M. M.A. Sarker
    Department of Mathematics,
    Bangladesh University of Engineering and Technology
    Dhaka-1000, Bangladesh
    Abstract:
    This article deals with the thermodynamic optimization of a solar driven sorption
    refrigeration system. An externally irreversible but internally endo-reversible model has
    been emp loyed to analyze the optimum conditions of a sorption cooling system driven by
    a solar collector. The operating conditions for maximum refrigeration load are
    determined. It is shown that the system gives its highest capacity if the thermal
    conductances of the heat exchangers are distributed properly. Results also show that
    optimum refrigeration load increases with the increase of collector stagnation and
    required room temperature increase and decreases as the ratio of collector size to the
    cumulative size of all four heat exchangers increases. It may also see that the optimal
    thermal conductance of the evaporator expands with the expense of the optimal thermal
    conductance of solar collector as collector stagnation temperature, refrigerated room
    temperature increase.
    1. Introduction
    In recent years, heat driven sorption refrigeration system have drawn considerable
    attention due to its lower environmental impact and large energy saving potential.
    Another interesting feature of this system is that, the chiller/heat pump can be operated
    by thermal heat such as waste heat from industries or by solar heat. From this context, a
    number of researchers investigated the performance of sorption heat pumping/
    refrigeration system driven by waste heat or by renewable energy sources. Among these,
    for solar cooling, worked by Pons and Guilleminot(1986 ), Zhang and Wang (1997) for
    automobile cooling and Saha et. al (2000), Alam et. al. (200a,b) for waste heat utilization.
    While the feasibilty of the system performance has been studied, the investigation on
    optimum design of a heat driven refrigeration system is scare. In 1993, Sokolov and
    Hersagal (1993) apply optimization techniques to optimize the system performance of a

    solar driven year round ejector refrigeration. Vargas
    et. al. (1996) investigated the

    optimal condition for a refrigerator driven by solar collector considering the three heat
    transfer irreversibilites. Later, Chen and Schouten (1998) discussed the optimum
    performance of an irreversible absorption refrigeration cycle in which three external heat
    transfer irreversibilities have been considered.
    Recently, Alam et. al. (2001) modeled and optimized a solar driven endo-reversible
    adsorption refrigeration system by considering the four heat transfer irrevesibilities. In
    that article, authors showed that the maximum refrigeration effect could be achieved by
    allocating the heat exchangers inventory properly. They also showed that the optimal
    thermal conductance of the heat exchangers that take heat from the heat source is almost
    equal to the thermal conductance of the heat exchangers that release to the external
    ambient. In the present study, the model of Alam et. al. (2001) has been utilized to
    investigate the optimum refrigeration load in different conditions. The primary objective
    of this study is to determine the optimum allocation of thermal conductancee between the
    collector and evaporator.
    2. Mathematical Model
    The main components of a solar driven sorption refrigeration system are a solar collector,
    a desorber, a sorber, a condenser and an evaporator, as shown in Fig. 1. In a sorption
    cycle, the working fluid execute a cycle and exchange heat to the heat exchange
    equipment of the system. During the cycle, desorber receives the heat load,



    QH, from the

    heat source (solar collector) at temperature,



    TH, while evaporator seizes heat load, QEVA,

    from the refrigeration space at temperature,



    TL; the condenser and evaporator release heat

    transfer,



    QCON and QA respectively to the external ambient at temperature, T0. In this

    analysis, it is assumed that there is no heat loss between the solar collector and the
    desorber and no work exchange occurs between the refrigerator and its environment.
    According to Alam et. al. (2001), the system can be described by the following non-
    Condenser Desorber
    Evaporator Sorber
    Solar



    QH ar collector

    Q



    CON

    Q



    EVA QA

    G



    Here
    B is the size of the collector relative to the cumulative size of the four heat

    exchangers and x, y and z are conductance allocation ratios, defined as



    = EVA , = H , and = A (9)

    According the constraint property of thermal conductance



    UA in equation (11), the

    thermal conductance distribution ratio for the condenser can be written as,
    ( )
    x y z
    UA
    UA
    v



    = CON = 1- - - (10)

    Here, it is assumed that sum of all thermal conductances are fixed,
    UA



    = (UA)H + (UA)A + (UA)CON + (UA)EVA (11)

    3. Optimization Techniques
    To maximize the refrigeration load,



    Q EVA , one needs to solve the nonlinear set of

    Equations (1)-(7). Newton-Raphson’s method with appropriate initial guesses was
    employed for solving the above set of non-linear equations. The Newton’s method has
    been employed to maximize



    Q EVA by optimizing tH, x, y and z and varying some

    selected parameters to generate the results shown in Figs. 2-4. The convergence criteria
    for both maximization technique and solving nonlinear set of equation is taken as
    ½



    R½2£10-7. Where, ½R½2 stands for the Euclidean norm of the residual vector. The

    results obtained by this numerical method are presented and discussed in the following
    section.
    Results and Discussion
    It is reported that the sorption refrigeration system can be operated by mid to lower
    driving heat source temperatures, T



    H (60 ~ 200 ºC), for producing refrigeration load

    temperatures, T



    L, between –15 ºC and 15 ºC [Alam et. al (2001)]. In terms of nondimensional

    form, these ranges can be estimated, respectively, as 1.1-1.5 for the driving
    heat source temperature and 0.8-0.95 for the refrigeration load temperature. Therefore,
    the dimensionless collector stagnation temperature,



    tst, has been varied from 1.1 to 1.5,

    and the dimensionless refrigeration space temperature,



    tL, has been set from 0.8 to 1.

    Alam et. al.(2001) showed that half of the total thermal conductance is distributed
    between the thermal conductances of collector and evaporator. From this viewpoint, this
    paper investigates the proper allocation of thermal conductances between the collector
    and evaporator. The optimum allocation of thermal conductances between collector and
    evaporator are indicated by shaded and non shaded parts in Figs.2-4.
    Fig.2 shows the effect of collector stagnation temperature on the optimum refrigeration
    load. It can be seen that the optimum refrigeration load, Q



    EVA increases with the increase

    of collector stagnation temperature. This is accord with the real situation. Because, the
    system can be operated effectively with the high heat source temperature, which leads the
    cooling load to increase. This figure also depicts the optimal allocation between the
    thermal conductance ratios of collector and evaporator. From Fig. 2, it can also be
    observed that optimum evaporator thermal conductance is proportional to collector
    stagnation temperature while optimum collector thermal conductance is inversely
    proportional to collector stagnation temperature.
    The effects of dimension collector size



    B on the optimal refrigerator load are depicted in

    Fig. 3. It can be seen that an increase in dimensionless collecdtor size,



    B leads the optimal

    refrigeration load to increase. Actually an increase in collector size leads the system to
    supply heat effectively, which causes the system to increase the refrigeration load. It can



    0 Not allowed!



  
صفحة 6 من 83 الأولىالأولى ... 23456789101656 ... الأخيرةالأخيرة
الكلمات الدلالية لهذا الموضوع

عرض سحابة الكلمة الدلالية

RSS RSS 2.0 XML MAP HTML

Search Engine Optimization by vBSEO ©2011, Crawlability, Inc.