GOVERNMENT ENGINEERING COLLEGE, VALSAD

Department ofChemical Engineering

GUIDED BY :-1) MR. GUNJAN KAPADIA

2) PROF. ANKIT PATEL

PREPARED BY:

DHAVAL P. BUTANI (110190105050)

BHAGIRATH V. JALELA (120190105050)

HARSH D. PATEL (120190105061)

DINESH B. JAGTAP (120190105062)

KRUNAL B. SHEKHADA (120190105064)

Topic Study of different parameters for optimum

design of solar heated pipe with parabolic trough reflector.

Introduction :- We know that the solar energy is a very important source. Solar energy collector is a device for collecting solar radiation and

transfers the energy to the fluid passing in contact with it. Solar energy requires solar collectors. These are general two types:- (1) non concentrating or flat plate type solar collector. (2) concentrating(focusing) type solar collector. The solar energy collector, with its associated absorber, is the

component of any system for the conversion of solar radiation energy into more usable (e.g. heat or electricity).

In non-concentrating type, the collector area is the same the absorber area.

Principle:-

The principle of the parabolic trough collector, which is often used in concentration collector, is shown by the cross-section in fig. Solar radiation coming from the particular direction is collected over the area of the reflecting surface and is concentrated at the focus of the parabola. If the reflector is in the from of a trough with parabolic cross-section, the solar radiation is focused alone a line. Mostly cylindrical parabolic concentrators are used, in which absorber is placed along focus axis. Fig.2) General Mechanism

Aluminium Sheet ( Parabola )

As shown in fig.2, here the reflective sheet is made by an aluminium with 0.6 mm in thickness.

We used the aluminium sheet as a reflector because it is cheapest and easily available in market as well as it’s reflectivity is very good as compare to other material.

Here, there are two different sheet are available so we have to joint the sheet and give the parabola shape.

Fig. 3) The Aluminium sheet

As shown in fig.3 the parabolic trough collector is made by the bending an aluminum sheet of reflective material into a parabolic shape.

A metal copper tube pipe coated with black zinc, covered with glass tube to reduce the heat losses, is place along the focal line of the collector. When parabola is placed towards the sun the parallel rays incident on the reflector are reflected and focused onto the receiver tube.

The concentrated radiation reaching the receiver tube heats the fluid that circulates through it, thus transforming of solar radiation into useful heat. It is a sufficient use of single axis tracking of sun and thus long collector modules are created.

Fig.4) General Mechanism

Receiver Pipe :- Fig.5) shows the metal copper tube coated with black zinc, covered with glass tube to reduce the heat losses, is place along the focal line of the collector. The surface of the tube is coated with black zinc, because that has a high absorptance of solar irradiation and a low emittance for thermal radiation. Hence, the selective coating increase the temperature of the absorbing material.

Fig. 5) Copper tube coated with black zinc

SELECTIVE ABSORBING COATINGS:- An efficient way to reduce thermal losses from the absorber plate of a solar

heating panel is by using selective absorber coating. An ideal selective coating is one that is a perfect absorber of solar radiation

while being a perfect reflector of thermal radiation Such a coating will make a surface, a poor emitter of thermal radiation.

Hence a selective coating increase the temperature of the absorbing material. If back losses of an absorbing surface are absent, the steady-state condition

give :

Solar flux absorbent = Thermal flux emitted

The absorptance and emittance of radiation at given wavelength are equal. A selective surface is a surface that has a high absorptance for short wave

radiation ( less than 2.5µm ) and a low emittance of long wave radiation ( more than 2.5µm ).

A large number of non-selective coating are available and are in widespread use as flat-plate collector coating.

Most of these coating have absorptances exceeding 0.95 and emittances of 0.90-0.95.

Table lists properties of some selective coatings.

Selective coating properties:-

Glass Envelope:-

Fig. 6) shows that the Glass envelope, it placed around the absorber tube to reduce the convectional heat loss from the receiver and thereby further reduce the heat loss coefficient. Here, we used the air in the glass tube rather than the vacuum because creating the vacuum is very difficult and as well as it is very costly. As we glass cover then more and more heat Fig. 6) Glass tube absorbed and increased the temperature of the fluid flowing through the pipe. Fig. 7) shows the general mechanism of the tube and glass envelope.

Fig. 7) General Mechanism

PROPERTIES OF GLAZING MATERIAL:-

General Materials:-

Fig. 8) shows General material used for joining the pipe. The bottom fig. joint at the end of the pipe at which the hole is provided. In this hole we have to put the thermometer which indicate the temperature of the fluid, flowing through the pipe.

Fig. 8) General Material

Fig 9) The Whole Design of Model

Design of parabolic trough reflector:-

Design of depth: Now the design of depth(d) in team of focal length (f), d=D2/16f Where, d= depth, D= diameter, f= focal length.  Now, find focal length; f=D2/16dCalculating f/d ratio: f/d ratio use for the find the focal length. f/d ratio is easy to find this equation; f/d=1/4tan(θ/4) where, θ is the beam width in degrees.

Design of solar heated pipe (receiver):-

Solar heated pipe very imported part of the system. pipe area are calculated equation is:

A=6.28 r l Where , l= length of the pipe, And r= radius of the pipe . Now the inside diameter of the pipe (Di) and the thickness of pipe t then find the

outside diameter (D0): D0= Di + t Other the vernier caliper is use for find the diameter of the pipe.

THANK YOU FOR YOUR TIME & ATTENTION…