Calculating Solar Radiation Received by Tubular Collectors

1995 ◽  
Vol 117 (4) ◽  
pp. 341-344 ◽  
Author(s):  
R. Perez ◽  
R. Seals ◽  
J. Anderson ◽  
D. Menicucci
Keyword(s):  
Low Temperature ◽  
Solar Radiation ◽  
Flat Plate ◽  
Solar Collectors ◽  
The Subject ◽  
Evacuated Tubes ◽  
The Difference ◽  
Tubular Arrays

Tubular absorbers installed inside evacuated tubes represent an increasingly common design for low-temperature solar collectors. Much work has been done on the subject of solar radiation received by flat-plate collectors; much less has been done for tubular collectors. In this paper we present an algorithm to estimate irradiance impinging on tubular arrays. Key examples are provided to illustrate the difference of energy collected between flat-plate and tubular collectors.

Economic Optimization of Stationary Nonevacuated CPC Solar Collectors

1987 ◽  
Vol 109 (1) ◽  
pp. 40-45 ◽  
Author(s):  
M. J. Carvalho ◽  
M. Collares-Pereira ◽  
J. M. Gordon
Keyword(s):  
Low Temperature ◽  
Flat Plate ◽  
Operating Temperature ◽  
Solar Collectors ◽  
Economic Optimization ◽  
Promising Alternative ◽  
Energy Delivery ◽  
Low Concentrations ◽  
East West ◽  
Concentration Ratios

Stationary, nonevacuated CPC solar collectors are a promising alternative to corresponding flat plate collectors in that they offer superior yearly energy delivery at comparable cost for low-temperature thermal applications. For realistic cost scenarios, we determine optimal concentrator configurations and concentration ratios, and calculate their sensitivity to variations in relative component costs, climate, orientation and collector operating temperature. For CPC’s that are to have the flexibility of either east-west or north-south orientation, optimized collectors are shown to have low concentrations of around 1.2, achieved by truncation from acceptance half angles of about 45 deg.

Solar Radiation Model Applied to a Low Temperature Evacuated Tubes Solar Collector

2018 ◽  
Vol 141 (3) ◽  
Author(s):  
Oscar A. López-Núñez ◽  
J. Arturo Alfaro-Ayala ◽  
J. J. Ramírez-Minguela ◽  
J. Nicolás Flores-Balderas ◽  
J. M. Belman-Flores
Keyword(s):  
Low Temperature ◽  
Solar Radiation ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Solar Collector ◽  
Outlet Temperature ◽  
Radiation Model ◽  
Solar Radiation Model ◽  
Evacuated Tubes

A solar radiation model is applied to a low temperature water-in-glass evacuated tubes solar collector to predict its performance via computational fluid dynamics (CFD) numerical simulations. This approach allows obtaining the transmitted, reflected, and absorbed solar radiation flux and the solar heat flux on the surface of the evacuated tubes according to the geographical location, the date, and the hour of a day. Different environmental and operational conditions were used to obtain the outlet temperature of the solar collector; these results were validated against four experimental tests based on an Official Mexican Standard resulting in relative errors between 0.8% and 2.6%. Once the model is validated, two cases for the solar collector were studied: (i) different mass flow rates under a constant solar radiation and (ii) different solar radiation (due to the hour of the day) under a constant mass flow rate to predict its performance and efficiency. For the first case, it was found that the outlet temperature decreases as the mass flow rate increases reaching a steady value for a mass flow rate of 0.1 kg/s (6 l/min), while for the second case, the results showed a corresponding outlet temperature behavior to the solar radiation intensity reaching to a maximum temperature of 36.5 °C at 14:00 h. The CFD numerical study using a solar radiation model is more realistic than the previous reported works leading to overcome a gap in the knowledge of the low temperature evacuated tube solar collectors.

Heat Exchanger Theory Applied to the Design of Water- and Air-Heating Flat-Plate Solar Collectors

1988 ◽  
Vol 110 (2) ◽  
pp. 132-138 ◽  
Author(s):  
Gregory J. Kowalski ◽  
Arthur R. Foster
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Flat Plate ◽  
Solar Collector ◽  
Operating Conditions ◽  
Solar Collectors ◽  
Heat Transfer Characteristics ◽  
Air Heating ◽  
Collector Efficiency ◽  
The Difference

A general method for the design of flat-plate solar collectors based on solar collector theory has been developed. It can be applied to both liquid- and air-heating solar collectors. The solar collector efficiency is determined by the product of the effectiveness (ε) and the insolation use factor (IUF). The effectiveness describes the heat transfer characteristics of the collector and is shown to be a function of a solar number of transfer units (SNTU) and a parameter ψ. For an air-heating collector, the ψ parameter equals the collector efficiency factor, while for a liquid-heating collector it must account for the difference between the plate and tube heat transfer areas. The effectiveness and SNTU parameters are similar to the effectiveness and NTU parameters used in heat exchanger design methods. The IUF is a measure of the operating conditions of the collector. It represents the difference between the transmittance-absorptance product and the ratio of the minimum heat loss to the insolation on the exterior cover. The relationship between the effectiveness and the SNTU parameter is general for all nonconcentrating collectors. One advantage of this method over the traditional Hottel-Whillier method is that it separates the heat transfer characteristics of the solar collector from its optical properties and the operating conditions.

On Optimizing Solar Collectors Orientation Under Daily Nonrandom Cloudiness Conditions

1988 ◽  
Vol 110 (4) ◽  
pp. 346-348
Author(s):  
M. Segal ◽  
R. A. Pielke ◽  
Y. Ookouchi
Keyword(s):  
Solar Radiation ◽  
Solar Energy ◽  
Flat Plate ◽  
Illustrative Case ◽  
Solar Collectors ◽  
Monthly Basis ◽  
Energy Gains ◽  
Geographical Locations

Seasonal daily nonrandom cloudiness is typical in many geographical locations. Optimization of flat-plate solar collectors orientation in such situations requires azimuth and tilt modifications from those when daily cloudiness is random. The present study evaluates the significance of optimizing solar radiation gains, while considerating an illustrative case of nonrandom afternoon/morning cloudiness. Results suggest that for fixed flat-plate collectors the related gain in solar energy is practically insignificant. For nonfixed collectors the solar energy gains can be improved on a monthly basis by up to ∼6 percent.

Using Adsorption Cooling and Thermal Solar Collection for Residential Cooling Applications in Canada

2018 ◽  
Author(s):  
Jordan McNally ◽  
Christopher Baldwin ◽  
Cynthia A. Cruickshank
Keyword(s):  
Water Temperature ◽  
Flat Plate ◽  
Flow Rate ◽  
Heating System ◽  
Cooling Capacity ◽  
Hot Water ◽  
Inlet Temperature ◽  
Solar Collectors ◽  
Adsorption Chiller ◽  
The Difference

An adsorption chiller is a type of chiller that uses heat input as the driving force for chemical compression of a refrigerant and provides cooling with low electrical consumption. An experimental setup was designed, instrumented, and constructed to meet constant inlet temperature and flow rate requirements for the commercially available adsorption chiller unit tested. Two types of tests were conducted, one with a constant hot water temperature which represents a district style heating system and another with a varying hot water temperature, representing a system using flat plate solar collectors. Numerous tests were run with constant inlet temperatures across the complete operating range of the chiller and at varying flow rates for each of the three main inputs. It was determined that variations in temperature had a much more significant impact on the performance of the chiller, compared to the variations in flow rate, which were almost negligible within tested range. Dynamic inlet temperature tests were run using the modified system which uses data from a weather file to simulate a system using flat plate solar collectors and vary the hot water inlet temperature to the system. The results showed that when the average hot water inlet temperature is lower than 60°C and higher than 75°C, the difference in performance between constant inlet temperature and dynamic inlet temperature tests was very small. However, the cooling capacity at 75°C was about 4 kWth greater than at 60°C. Majority of the test produced a thermal COP between 0.45 and 0.50. Therefore, based off the solar collector system’s capacity to maintain a suitable average hot water temperature, the cooling performance of the chiller can be deemed suitable for residential applications.

Learning Language Levels in Students Accurate with a History Academic Achievement History

2017 ◽  
Vol 1 (2) ◽  
pp. 137
Author(s):  
Noorlela Binti Noordin ◽  
Abdul Razaq Ahmad ◽  
Anuar Ahmad
Keyword(s):  
Academic Achievement ◽  
Statistical Inference ◽  
Quantitative Data ◽  
Quantitative Methods ◽  
Descriptive Statistics ◽  
Language Test ◽  
The Subject ◽  
The Difference ◽  
Learning Language ◽  
The Relationship

This study was aimed to evaluate the Malay proficiency among students in Form Two especially non-Malay students and its relationship to academic achievement History. To achieve the purpose of the study there are two objectives, the first is to look at the difference between mean of Malay Language test influences min of academic achievement of History subject among non-Malay students in Form Two and the second is the relationship between the level of Malay proficiency and their academic achievement for History. This study used quantitative methods, which involved 100 people of Form Two non-Malay students in one of the schools in Klang, Selangor. This study used quantitative data were analyzed using descriptive statistics and statistical inference with IBM SPSS Statistics v22 software. This study found that there was a relationship between the proficiency of Malay language among non-Malay students with achievements in the subject of History. The implications of this study are discussed in this article.

The Idea of a Meaningful Synthesis of Marxist and Non-Marxist Systems of Political Economy as a Mirror of Intellectual Turmoil (About V.T. Ryazanov’s Book «Modern Political Economy: Prospects of Neo-Marxist Synthesis»)

2019 ◽  
pp. 74-98
Author(s):  
A.B. Lyubinin
Keyword(s):  
Economic Theory ◽  
Political Economy ◽  
Economic Status ◽  
Economic Science ◽  
Objective Reality ◽  
Commodity Production ◽  
Subjective Assessments ◽  
The Subject ◽  
The Difference ◽  
Political Economic

Review of the monograph indicated in the subtitle V.T. Ryazanov. The reviewer is critical of the position of the author of the book, believing that it is possible and even necessary (to increase the effectiveness of General economic theory and bring it closer to practice) substantial (and not just formal-conventional) synthesis of the Marxist system of political economy with its non-Marxist systems. The article emphasizes the difference between the subject and the method of the classical, including Marxist, school of political economy with its characteristic objective perception of the subject from the neoclassical school with its reduction of objective reality to subjective assessments; this excludes their meaningful synthesis as part of a single «modern political economy». V.T. Ryazanov’s interpretation of commodity production in the economic system of «Capital» of K. Marx as a purely mental abstraction, in fact — a fiction, myth is also counter-argued. On the issue of identification of the discipline «national economy», the reviewer, unlike the author of the book, takes the position that it is a concrete economic science that does not have a political economic status.

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