The thesis presents analytical and experimental methods of studying various aspects of the optical and thermal performance of a transwall passive solar system. Some of these methods are applicable to other solar systems. Two ray-tracing techniques, 1-dimensional and 3-dimensional, are presented for an accurate calculation of the optical properties of a transwall module with its outside glass plate(s). These techniques calculate not only the reflected, absorbed or transmitted fractions of the incident radiation but also the spectrum of the transmitted radiation. This information is required for a better assessment of the transwall system as an illuminating source and as a thermal system. Both techniques are applied to a particular transwall module with one outside glass plate and the importance of various features of the incident solar radiation (such as spectrum, angular variation, polarization, etc.) are discussed. The difficulties associated with the nature of the diffuse solar radiation coming from the sky, or the ground , are overcome by employing a discretization method in which the continuous diffuse radiation is divided into discrete pencils of radiation. An analytical thermal model of a passive solar system is presented and its verification is established by using a test-box containing a full size transwall module. The outcome of this verification is satisfactory given the uncertainties of the optical and thermal properties of the various elements of the test-box. The success of the analytical modelling depends on accounting for the 3-dimensional solar radiation field outside and inside the passive solar system. The methods developed, accompanied by the two ray-tracing techniques, allow for an accurate distribution of the total incident radiation among the semitransparent elements and the external and internal surfaces of any passive system. The method of distributing the solar radiation among the internal surfaces of an enclosure is applied to the convex parallelepiped enclosure of the test-box and, as additional example of the method, also applied to the non-convex enclosure of a typical glasshouse with E-w transwalls. The phenomenon of the natural convection of a fluid inside a transwall module induced by the absorption of radiation is predicted by a numerical method, first introduced by Patankar. Examples of the temperature, pressure and velocity fields of three transwall modules filled with distilled water under the irradiance conditions of 400 to 500 W/m2 are presented. By introducing the effective conductivity concept the complicated phenomenon of the fluid convection inside the module is simplified to a conduction phenomenon. This is also necessary for the long term-days or months - analytical modelling of the total transwall passive system because the numerical prediction of the former phenomenon requires an excessive amount of computer time. The calculation of the effective conductivity is obtained by employing an analytical approach which makes use of the data collected from the application of the numerical method, mentioned above. Values of the ratio of the effective conductivity to the conductivity of the still water are calculated at two interfaces inside the water of four different transwall modules. Measurements of the temperature and the velocity at certain points in a small transwall module irradiated by a solar simulator have been performed to support some of the numerical predictions.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:329511 |
| Date | January 1983 |
| Creators | Paparsenos, George F. |
| Publisher | University of Glasgow |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://theses.gla.ac.uk/8593/ |
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