Solar Ray Collector

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OBJECTIVE:

- To determine the efficiency of the solar ray collector under various experimental conditions.

1. Illumination with halogen lamp. Water temperature θe≈ 20°C.

a) Complete collector
b) Collector without glass plate
2. Illumination with halogen lamp. Water temperature θe ≈60°C.

c) Complete collector
d) Complete collector, cold jet of air impinges
e) Collector without glass plate
f) Collector without glass plate, cold jet of air impinges

INTRODUCTION:

Solar ray collectors transform solar radiation into heat and transfer that heat to water. Then solar heat can be used for heating water, to back up heating systems. The heart of a solar collector is the absorber, which is usually composed of several narrow metal strips. The carrier fluid for heat transfer flows through a heat-carrying pipe, which is connected to the absorber strip. In plate-type absorbers, two sheets are sandwiched together allowing the medium to flow between the two sheets. Absorbers are typically made of copper or aluminum.

CALCULATION:

Important formula for calculating the useful power, PN and efficiency, η:

1. Useful power, PN = c · m · (θo - θi)

where, m = 100 g/min = 1.667 x 10-3 kg/s
c = specific thermal capacity of water = 4.182 kJ/kg · K
θo = average absorber outlet temperature
θi = average absorber inlet temperature

2. Efficiency, η = PN / (qi x A)

where, qi = 1 kW/m2
A = 0.12 m2
Sample calculation:

PART A

I. Complete collector ( t=15 min )
- useful power, PN = c · m · (θo - θi)
= (4.182 kJ/kg · K) · (1.667 x 10-3 kg/s) · (32.5 – 28.5) K
= 0.0279 kW
- efficiency, η = PN / (qi x A)
= 0.0279kW / (1 kW/m2 x 0.12 m2)
= 0.232

II. Complete without glass plate ( t=15min )
- useful power, PN = c · m · (θo - θi)
= (4.182 kJ/kg · K) · (1.667 x 10-3 kg/s) · (35.0 - 30.0) K
= 0.0348 kW

- efficiency, η = PN / (qi x A)
= 0.0279kW / (1 kW/m2 x 0.12 m2)
= 0.29

PART B

I. Complete collector ( t=15 min )
- useful power, PN = c · m · (θo - θi)
= (4.182 kJ/kg · K) · (1.667 x 10-3 kg/s) · (50.0 -50.5) K
= 3.49 W
- efficiency, η = PN / (qi x A)
= 3.49W / (1 kW/m2 x 0.12 m2)
= 0.029

II. Collector without glass plate ( t=10min )
- useful power, PN = c · m · (θo - θi)
= (4.182 kJ/kg · K) · (1.667 x 10-3 kg/s) · (52.0 -52.0) K
= 0.0 W

- efficiency, η = PN / (qi x A)
= 0.0 W / (1 kW/m2 x 0.12 m2)
= 0.0

III. Complete collector, cold jet of air impinges ( t=15 min ) - useful power, PN = c · m · (θo - θi)
= (4.182 kJ/kg · K) · (1.667 x 10-3 kg/s) · (51.5-51.5) K
= 0.0 W
- efficiency, η = PN / (qi x A)
= 0 W / (1 kW/m2 x 0.12 m2)
= 0.0

IV. Collector without glass plate , cold jet of air impinges ( t=15min ) - useful power, PN = c · m · (θo - θi)
= (4.182 kJ/kg · K) · (1.667 x 10-3 kg/s) · (43.0 - 49.0) K
= 0.0418 kW

- efficiency, η = PN / (qi x A)
= 0.0418 kW / (1 kW/m2 x 0.12 m2)
= 0.349

DISCUSSION:

In this laboratory session, we have conducted an experiment regarding Solar Ray Collector. The main idea of this experiment is to determine the efficiency of the solar ray collector under various experimental conditions. Theoretically, solar collectors transform solar radiation into heat and transfer that heat to a medium (water, solar fluid, or air). Then solar heat can be used for heating water, to back up heating systems. The efficiency of a solar collector is defined as the quotient of usable thermal energy versus received solar energy. Absorbers are usually black, as dark surfaces demonstrate a particularly high degree of light absorption. The level of absorption indicates the amount of solar radiation being absorbed that means not being...
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