Documents

Renewable Energy Make-Up Exam

Categories
Published
of 6
All materials on our website are shared by users. If you have any questions about copyright issues, please report us to resolve them. We are always happy to assist you.
Related Documents
Share
Description
Final
Transcript
  Pharos University in Alexandria ME-333 Renewable Energy & Faculty of Engineering Storage Systems Mechanical Engineering Department Spring 2013 - 2014 8  th  Semester  Make-Up Exam  Answer All Question Time : 1 Hour  Assume Any Missing Data Question (1) a)   Show how the blade of a Horizontal axis wind turbine is twisted from tip to root. b) Compare the efficiency of flat plate collector and parabolic trough collector showing which of them is higher. Question (2) An array of 10 solar flat-plate collector modules installed in parallel; each has an absorbing area of 8    2 , a heat removal factor of 0.8 & an overall loss coefficient of 8  /  2 ℃  .They are connected to a water storage tank of 2  3  , which is initially at 40 ℃  . The storage tank loss coefficient-area product is 1.9 W and the tank is located outside. If the load flow is 1.667    , and the make-up water is at 20   ℃ , calculate the performance of this system for the four-hour period shown in the following table Hour S(MJ/  2 )   ( ℃ )  9-10 3.56 17.2 10-11 3.8 18.1 11-12 4.0 19.5 12-13 4.2 21    Question (3) A cylindrical parabolic concentrator with width 5 m and length 50 m has an absorbed radiation per unit area of aperture of 600 W/  2 . The receiver is a cylinder pained flat black and surrounded by an evacuated glass cylindrical envelope. The absorber has a diameter of 70 mm, and the transparent envelope has a diameter of 110 mm. The collector is designed to heat a fluid entering the absorber at 200 ℃  at a flow rate of 0.18 kg/s. the fluid has     =3.26  / ℃ . The heat transfer coefficient inside the tube is 300  /  2 ℃  and the overall loss coefficient is 12  /  2 ℃ . The tube is made of stainless steel (  =16  / ℃ ) with a wall thickness of 5 mm. if the ambient temperature is  25 ℃ , calculate the useful gain and exit fluid temperature. Question (4) For a site in Egypt with a most frequent wind speed of 9 m/s, you are requested to design a wind turbine used for pumping 22  3 / ℎ  of water to a head of 22 m. For this purpose find: i)   The rotational speed of the wind turbine ii)   The wheel diameter iii)   The axial thrust Parabolic Concentrator F ′ =1U L 1U L +D o h f i D i +  D o 2k lnD o D i      F ′′ =F R F ′ =m  ̇ C P A r U L F ′  1  e −A  U  F  m ̇ C       Q u =F R  ∗ A a  ∗ [S  A r A a U L (T i   T a )]   Storage Tank Q u =F R  ∗ A c  ∗ [S  U L (T i   T a )]   T s+ =T s + ∆ t  � mc p  s [Q u   L s   (UA) s (T s   T a′ )]   Wind Turbine  =  12     (  2   2 )  ;   =4  (1  2 ) ;   =    (      )    Pharos   University    in    Alexandria   ME  ‐ 333   Renewable   Energy    &   Faculty    of    Engineering   Storage   Systems   Mechanical    Engineering   Department    Spring   2013  ‐ 2014   8  th   Semester     Make-Up Exam Solution Question (1) a)   The   magnitude   and   direction   of    the   relative   wind   angle   ,   varies   along   the   length   of    the   blade   according   to   the   local   radius,   r.   This   is   because   the   local   tangential   speed,   u,   of    a   given   blade   element   is   a   function   of    the   rotor’s   angular   velocity   Ω   times   the   local   radius,   r,   of    the   blade   element.   As   the   tangential   speed   decreases   towards   the   hub,   the   relative   wind   angle      progressively   increases.   If    a   blade   is   designed   to   have   a   constant   angle   of    attack   along   its   length,   it   will   have   to   have   a   built ‐ in   twist,   the   amount   of    which   varies   progressively   from   tip   to   root,   the   figure   below   demonstrates   the   progressive   twist   of    HAWT   rotor   blade.   b)   The   student   has   to   show   that   the   efficiency   for   the   flat   plate   collector   is   related   to   the   total   radiation   (direct   +   diffuse)   while   it   is   related   to   the   direct   radiation   only   in   the   case   of    parabolic   trough   collector.   For   flat   plate   collector   optical   losses   are   considerably   small,   temperature   of    heat   loss   area   is   very   low   and   area   of    heat   transfer   is   materially   greater.   In   the   case   of    parabolic   trough   collector,   optical   losses   are   much   greater,   temperature   of    surface   losing   heat   is   considerably   greater,   but   area   of    heat   transfer   is   much   smaller.   Accordingly,   it   seems   that   flat   plate   collector   is   more   efficient.    Question (2) For   the   period   9    –   10   Q    F   ∗ A   ∗ S  U  T    T     A    8 ∗ 10  80  2   Q   ∗ ∆  0.8 ∗ 80 ∗ 3.56 ∗ 10    8 ∗ 3600∗40  17.2  1.85∗ 10      T    T    ∆tmc    Q    L    UA  T    T     T    40  12000∗ 4200  1.85 ∗ 10    1400288  40  17.2   62.02    Hour                   9    –   10   3.56   17.2 40 62.025997   10  ‐ 11   3.8   18.1 62.026 81.154127   11  ‐ 12   4   19.5 81.15413 97.839283   12 ‐ 13   4.2   21 97.83928 112.65022  
We Need Your Support
Thank you for visiting our website and your interest in our free products and services. We are nonprofit website to share and download documents. To the running of this website, we need your help to support us.

Thanks to everyone for your continued support.

No, Thanks