Essay: Design and fabrication of two symmetric CPC collectors without cover plate

Essay details:

  • Subject area(s): Environmental studies essays
  • Reading time: 5 minutes
  • Price: Free download
  • Published on: November 15, 2015
  • File format: Text
  • Number of pages: 2
  • Design and fabrication of two symmetric CPC collectors without cover plate
    0.0 rating based on 12,345 ratings
    Overall rating: 0 out of 5 based on 0 reviews.

Text preview of this essay:

This page of the essay has 1260 words. Download the full version above.

4.1 Introduction
This chapter focuses on the design and fabrication of two symmetric CPC collectors without cover plate, E-W oriented (south facing), for converting incident solar radiation to thermal energy. It consist a description steps of manufacturing Compound Parabolic Concentrators (CPCs) and a detailed explanation of how the individual components of the systems work. The design, implementation and testing of the systems were conducted in Kirkuk (280 km north of Baghdad).
4.2 Description of the CPCs
Two models of CPCs have been designed, manufactured and tested at totally sunny space. These models are consisted of a support structure that allows to position the CPCs at different angles, reflector parts assembly and evacuated tube absorbers as shown in fig. (4-1). The geometrical characteristics of the designed CPCs, are given in Table (4-1).
Table (4-1) The geometrical characteristics of the designed CPCs.
Parameters Units 2.32?? CPC 3.84?? CPC
Acceptance half-angle degree 26 15
Truncation — Full CPC 20o 26o 59o
Geometric concentration ratio — 2.32 3.84 3.61 2.32
Aperture area m2 0.5119 0.8475 0.7973 0.5119
Aperture width m 0.3424 0.5669 0.5333 0.3424
Length of the CPC m 1.495 1.495
Figure 4-1: The schematic of CPC collectors.
4.3 Design of the Support Structure
CPC’s support structure consists of two group assemblies: stationary base assembly and the other tilting part assembly where the CPCs supported on.
4.3.1 Stationary Base Assembly
In order to undergo the hard weather conditions, and achieve the supporting requirement through the solar energy collectors operation, the fixed base has been made. The selection of the part materials is confirmed in order to meet the above requirements as declared the materials Steel square bars as shown in fig. (4-2).
Figure 4-2: The stationary base (main base) of the structure support of CPCs.
4.3.2 The Tilting Part Assembly
The support structure must be allow to position the CPCs at different tilt angles, so the CPCs have one group of the tilting part assembly for slope adjustment, it’s containing three barrel hinges and steel square tubes as shown in fig. (4-3). The mentioned parts were supported by the base, must lead to perform the function of the assembly (tilting motion) properly and successfully.
Figure 4-3: The tilting part of the structure support of CPCs.
4.4 Design of the Reflector Parts Assembly
The reflector is designed to set the acceptance half angle 15o and truncated in three levels, to 20o (3.84?? CPC), 26o (3.61?? CPC) and 59o (2.32?? CPC) as illustrated in figure (4-4), and second reflector is designed to set acceptance half angle 26o (2.32?? CPC) as illustrated in figure (4-5).
Figure 4-4: illustration of designed 3.84?? CPC.
Figure 4-5: illustration of designed 2.32?? CPC.
The whole assembly consists of two secondary assemblies as
below:
A. The Compound Parabolic Base Assembly: it is made of steel flat bars and steel square tubes which takes a compound parabolic form, exactly the same as the reflecting form as shown in fig.(4-6). This assembly must be accurate by making reference template made of acrylic sheet, then using accurate profile machine to fabricate the required form depending on the reference template.
Figure 4-6: Welding reflector base parts.
B. The Reflector Assembly: the aim of this assembly is to reflect all the solar rays within wide range of acceptance half-angle and concentrate them on the receiver. It is made of aluminum plate with thickness of 0.6 mm and solar mirror film with self-back adhesive then glued together. The solar mirror film has been selected because it has good reflectivity (figure 4-7 shows the reflectance of the solar mirror film) , non-corrosive, available and not expensive. Aluminum plate easily to perform. The aluminum plate must be supported by the compound parabolic base assembly and takes its form exactly.
Figure 4-7: The reflectance of the solar mirror film.
4.5 Ray tracing model validation
In order to investigate the heat flux with the incidence angle, the ray-tracing code TRACE PRO is used. Ray-tracing is done for different incidence angles (0o, 10o, 20o and 30o) for CPCs: 2.32?? CPC (??c=26o), 3.84?? CPC (??c=20o) and 3.61?? CPC (??c=26o) to simulate the rays those incident on the apertures of CPCs. Also the ray-tracing is done for 2.32?? CPC (??c=59o), but with different incidence angles (0o, 20o, 40o and 60o) because it has larger half acceptance angle than those for other three CPCs.
Figure (4-8) shows the ray-tracing for 2.32?? CPC (??c=26o) with incidence angles (0o, 10o, 20o and 30o), for incidence angles (0o, 10o and 20o) all rays incident on the aperture within the acceptance angle reached the absorber. For incidence angles (30o) all rays with ?? > ??c traveled back eventually from the aperture.
Figure (4-8a): Ray-tracing for 2.32?? CPC (??c=26o) with incidence angle (0o).
Figure (4-8b): Ray-tracing for 2.32?? CPC (??c=26o) with incidence angle (10o).
Figure (4-8c): Ray-tracing for 2.32?? CPC (??c=26o) with incidence angle (20o).
Figure (4-8d): Ray-tracing for 2.32?? CPC (??c=26o) with incidence angle (30o).
Figure (4-9) shows the ray-tracing for 3.84?? CPC (??c=20o) with incidence angles (0o, 10o, 20o and 30o), for incidence angles (0o, 10o and 20o) all rays incident on the aperture within the acceptance angle reached the absorber. For incidence angles (30o) all rays with ?? > ??c traveled back eventually from the aperture.
Figure (4-9a): Ray-tracing for 3.84?? CPC (??c=20o) with incidence angle (0o).
Figure (4-9b): Ray-tracing for 3.84?? CPC (??c=20o) with incidence angle (10o).
Figure (4-9c): Ray-tracing for 3.84?? CPC (??c=20o) with incidence angle (20o).
Figure (4-9d): Ray-tracing for 3.84?? CPC (??c=20o) with incidence angle (30o).
Figure (4-10) shows the ray-tracing for 3.61?? CPC (??c=26o) with incidence angles (0o, 10o, 20o and 30o), for incidence angles (0o, 10o and 20o) all rays incident on the aperture within the acceptance angle reached the absorber. For incidence angles (30o) all rays with ?? > ??c traveled back eventually from the aperture.
Figure (4-10a): Ray-tracing for 3.61?? CPC (??c=26o) with incidence angle (0o).
Figure (4-10b): Ray-tracing for 3.61?? CPC (??c=26o) with incidence angle (10o).
Figure (4-10c): Ray-tracing for 3.61?? CPC (??c=26o) with incidence angle (20o).
Figure (4-10d): Ray-tracing for 3.61?? CPC (??c=26o) with incidence angle (30o).
Figure (4-11) shows the ray-tracing for 2.32?? CPC (??c=59o) with incidence angles (0o, 20o, 40o and 60o), for incidence angles (0o, 20o and 40o) all rays incident on the aperture within the acceptance angle reached the absorber. For incidence angles (60o) all rays with ?? > ??c traveled back eventually from the aperture.
Figure (4-11a): Ray-tracing for 2.32?? CPC (??c=59o) with incidence angle (0o).
Figure (4-11b): Ray-tracing for 2.32??CPC (??c=59o) with incidence angle (20o).
Figure (4-11c): Ray-tracing for 2.32??CPC (??c=59o) with incidence angle (40o).
Figure (4-11d): Ray-tracing for 2.32??CPC (??c=59o) with incidence angle (60o).
4.6 The Form of the CPCs
The two constructed CPCs, 2.32?? CPC and 3.84?? CPC are shown in figure (4-12).
Figure (4-12): The form of the two CPC systems.
4.7 Evacuated Tube Absorber
Evacuated tube is composed of two coaxial borosilicate glass tubes fig. (4-13) with one open end for inlet and outlet and the another end sealed; the outer of 58mm diameter (1800mm) length (cover tube) and the inner 47mm diameter and (1720mm) length (absorbing tube). The thickness of the inner tube and outer tube is 1.6mm. The inner tube exterior is coated by selective coating (Aluminum Nitrite) in order to increase the absorptivity. The space between the two tubes is evacuated from the air to prevent the heat losses which resulted from the convection and conduction. Thus the absorbed solar energy is converted to heat and transmitted to fluid. Evacuated tube specifications are given in Table (4-2).
Figure (4-13): Schematic diagram of the Evacuated tube elements.
Table 4-2: Evacuated tube specifications.
Parameters Units Values
Receiver length mm 1800
Cover diameter mm 58
Absorber diameter mm 47
Cover Transmittance % 91
Coated surface absorptance % 93
Coated surface emittance % <8 Pressure of vacuum space Pa 5??10-3 Heat Loss W/m2' < 0.8 Insolation Temperature ' 250 Start-up Temperature ' ' 25 Life Time years 15 4.8 Design of the Thermal Storage Tank The design of the storage tanks for the CPCs consisted of : ' The inner and outer containers are made of plastic with thickness of 2.5 mm. The first used for containing the storage fluid, and the last used for fixing the insulator around the inner container. ' The polystyrene with thickness of 2.5 cm was used as insulator in order to decrease the losses as low as possible. ' The water is used as working fluid. 4.9 Apparatus and Instrumentation The experimental instruments, which have been used to investigate the performance of CPCs, can be classified into: 1- Thermocouples: Thermocouples are used to measure temperature at several locations in the system. The thermocouples were calibrated according to the mercury thermometer. 2- Thermocouples Selector Switch: Selector switch (20-way) is used to connect 8 thermocouples with the thermometer. 3- Digital Thermometer: Thermometer is used to read the value of temperature, and it's connected with the selector switch. 4- Solar Power Meter: The solar power meter is used to record the solar radiation on the CPCs. 4.10 Experimental Setup The experimental setup used for testing the fabricated CPCs are shown as a photo in figure (4-14). It consists of the constructed 2.32?? CPC, 3.84?? CPC, two 48 liter storage tanks, one for each CPC, and two recirculating pumps, with maximum mass flow rate of 0.02 kg/sec, the recirculation pump had two major functions, which were (i) to homogenize the water temperature in the storage tank, breaking up the stratification of the fluid, and (ii) circulating fluid through the CPC receiver tube a constant mass flow rate. A flexible tubes are used for conveyance of the working fluid. The pump recirculates the water from the storage tank through the evacuated tube receiver of the CPCs, then back to the storage tank. The water temperatures at inlet and outlet of the receiver tubes, the storage tanks temperature, and solar radiation intensity (beam and diffuse) are measured during the experiment. Figure (4-14): A photograph of CPCs setup.

...(download the rest of the essay above)

About this essay:

This essay was submitted to us by a student in order to help you with your studies.

If you use part of this page in your own work, you need to provide a citation, as follows:

Essay Sauce, Design and fabrication of two symmetric CPC collectors without cover plate. Available from:<https://www.essaysauce.com/environmental-studies-essays/essay-design-and-fabrication-of-two-symmetric-cpc-collectors-without-cover-plate/> [Accessed 19-11-19].

Review this essay:

Please note that the above text is only a preview of this essay.

Name
Email
Review Title
Rating
Review Content

Latest reviews: