Solar Collector Performance Analysis

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Questions and Answers

How does the heat removal factor (FR) account for the performance of a solar collector under operational conditions?

It only considers heat losses due to convection and ignores radiation losses.
It represents the ratio of the actual heat gain to the potential heat gain if the entire absorber plate were at the fluid inlet temperature. (correct)
It assumes the collector temperature is always equal to the ambient temperature.
It quantifies the ratio of the maximum possible heat gain to the actual heat gain.

In the context of solar collectors, plate effectiveness (Φ) is mathematically defined as tanh(m(w-D0)). How does this parameter influence the overall performance analysis of the collector?

It calculates the temperature difference between the fluid inlet and outlet.
It is used to estimate the incoming solar radiation (IT) on the collector surface.
It provides a measure of how efficiently heat is conducted from the absorber plate to the fluid tube. (correct)
It directly determines the overall heat loss coefficient (UL) of the collector.

The collector efficiency factor (F') relates to the actual and potential heat gain in a solar collector. What conditions would cause F' to approach its maximum possible value?

When the absorber plate temperature is significantly higher than the local fluid temperature.
When the absorber plate temperature is approximately equal to the local fluid temperature. (correct)
When the actual useful heat gain rate is minimized.
When the overall heat loss coefficient (UL) is maximized.

Which of the following parameters is NOT explicitly required for calculating the heat removal factor (FR) of a solar collector, assuming other necessary variables are known or can estimated?

Emissivity of the surrounding environment. (D) Signup and view all the answers

The overall heat loss coefficient (UL) is a critical parameter in solar collector analysis. How is UL fundamentally related to the various heat transfer mechanisms within the collector?

UL represents the sum of top loss, bottom loss, and side loss coefficients. (B) Signup and view all the answers

For simplifying the thermal analysis of solar collectors, certain assumptions are made. Which of the following is a typical assumption used to streamline the modeling process?

Plates and covers are treated as finite parallel surfaces. (D) Signup and view all the answers

In analyzing heat transfer from the absorber plate to the cover in a solar collector, which heat transfer mechanisms are predominantly involved?

Convection and re-radiation. (C) Signup and view all the answers

Radiation losses from a solar collector depend on several factors. Which of the following is NOT a direct influencing factor for these losses?

Fluid flow rate through the collector. (B) Signup and view all the answers

When evaluating the performance of solar collectors, the 'sky temperature' is often considered. How is sky temperature typically estimated in relation to ambient temperature (Ta)?

Sky temperature is equal to Ta - 6. (C) Signup and view all the answers

During the performance testing of a solar collector, which formula is used to calculate the useful heat energy gain (qu) from experimental data?

qu = m * Cp * (Tout - Tin) (B) Signup and view all the answers

Instantaneous efficiency (ηi) is a key metric in solar collector performance. How is it defined?

The ratio of useful heat gain to the product of incident radiation and collector area. (A) Signup and view all the answers

In the equation ηi = FR (AP/Ac)[(taualpha)avg – Ul/IT (Tin–Ta )], often used to express instantaneous efficiency (ηi), what do the terms (taualpha)avg represent?

The product of the transmittance of the cover and the absorptance of the absorber plate, averaged over the solar spectrum. (C) Signup and view all the answers

During experimental testing of solar collectors, certain environmental conditions are preferred to ensure reliable and consistent data. Which condition is generally recommended?

Wind velocity between 2 to 5 m/s. (B) Signup and view all the answers

When conducting performance tests on solar collectors, what is the allowable experimental error for the measurement of incident radiation (IT)?

±50 W/m² (A) Signup and view all the answers

The described performance test for solar collectors is based on which standard?

Indian standard value 12933 (A) Signup and view all the answers

Flat plate collectors (FPC) have several advantages. Which of the following is a key advantage that contributes to their widespread use?

Absorption of direct, diffuse, and reflected radiation. (C) Signup and view all the answers

Which statement best describes the operational characteristics of flat plate collectors (FPC) regarding their tilt and orientation?

FPCs typically have a fixed tilt and orientation, eliminating the need for tracking. (A) Signup and view all the answers

What makes flat plate collectors (FPC) cost-effective compared to other solar collector technologies?

Their simple design and ease of manufacturing contribute to lower costs. (B) Signup and view all the answers

Flat plate collectors (FPC) are typically best suited for which type of applications?

Low-temperature applications like domestic water heating and space heating. (A) Signup and view all the answers

Which of the following factors contributes MOST significantly to the long lifespan and relatively low maintenance costs associated with flat plate collectors (FPC)?

The absence of moving parts in their design. (A) Signup and view all the answers

Flashcards

Ideal Useful Heat Gains

Maximum heat gain when collector temperature matches inlet fluid temperature, minimizing losses.

Heat Removal Factor (FR)

Accounts for the reduction in useful energy gain due to heat losses.

FR Definition

The ratio of existing heat gain to potential heat gain if the plate temperature were at the fluid inlet temperature.