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[en] Two types of phase change materials were used as storage media in a Trombe Wall; namely paraffin wax (N-Eicoseue C20 H42) and Glaubers Salt (Na2SO410H2O). To investigate the performance of these materials, a theoretical model and a simulation programme were developed. The wall temperature, the amount of heat stored, and the optimum wall thickness were calculated for both types. The study found that using two sheets of glass on the outside wall increased the surface wall temperature by around 50 degree C. It also found that Glauber salt was a much better storage material than paraffin wax. For a selected winter day at a location of 32 oN latitude, the storage capacity of the salt was more than twice that of the paraffin wax. The salt storage capacity was 32816 kJ/m3 at an optimum wall thickness of 16 cm. this value for paraffin was 14464 kJ/m3 at 13 cm optimum thickness. The study also concluded that according to this high heating value the wall uses, Glauber salt as a storage medium could supply its heat to the surrounding for a much longer period at night
[en] Highlights: •A novel zero-energy TC-Trombe wall was introduced. •Experimental testing platform and numerical model were built. •The air heating and HCHO degradation performance were analyzed experimentally. •A photothermocatalytic synergetic effect existed in the solar driven TCO. •The total saving energy of 97.4 kW h/m2 be obtained in heating seasons in Hefei. -- Abstract: The present paper proposes a novel zero-energy solar application system combining the thermal catalytic technology with Trombe wall (TC-Trombe wall), which could realize indoor air purification and space heating simultaneously fully driven by solar energy. A full-day experiment was conducted to study the air heating performance and formaldehyde degradation performance of TC-Trombe wall. Results showed that the daily air heating efficiency was 41.3%. In our experiments, the generated total volume of fresh air and total formaldehyde degradation amount by TC-Trombe wall were 249.2 m3/(m2 day) and 208.4 mg/(m2 day), respectively. In addition, a photothermocatalytic synergetic effect exists in the solar light driven thermocatalytic oxidation process over MnOx-CeO2 catalysts. A dynamic numerical model was developed to predict system thermal properties. Based on the simulation results, the effects of the solar radiation intensity, ambient temperature and air layer thickness on the system thermal efficiency were discussed. Furthermore, the energy saving performance of TC-Trombe wall was evaluated in heating seasons in Hefei based the established system thermal model. Results showed that the total saving energy of up to 97.4 kW h/m2 could be obtained. The saving energy for space heating and formaldehyde degradation were 64.3 kW h/m2 and 33.1 kW h/m2, respectively.
[en] This work presents an analysis on heat transfer process occurred in the Trombe wall system with a new channel design in Yazd (Iran) on the coldest and warmest days of winter. The primary objective was to investigate the impact of heat transfer types on the temperature variation of the Trombe wall back and absorber throughout the day. For this reason, the variations of Rayleigh number, convective heat transfer coefficient, and the rate of convection, conduction, and radiation heat transfer exchanged with the Trombe wall have been studied. The analysis of Rayleigh number variations for the channel inside revealed that there is a noticeable decrease in the early hours expressing a discernible decrease in the temperature difference between the absorber and the channel space. At night time, the absorber and channel temperatures drop approximately to the same value. Furthermore, the role of conduction transfer is more sensible than that of convection in the early and late hours. However, the convection dominates at the midday. It should be noted that due to new channel design, the radiation heat transfer rate is maximum in the early and late hours. The heat transfer is more significant on the coldest day because of higher temperature difference between the different parts of the Trombe wall system. - Highlights: • Different heat transfer types were analyzed in Trombe wall with new channel design. • Highest amount of convection heat is delivered to the room during sunny period. • Radiation is the dominant heat transfer process from the Trombe wall. • Heat transfer is more sensible on the coldest day than the warmest day.
[en] Trombe Walls and solar chimneys are examples of passive solar air heating systems. However, the airflow and thermal efficiency characteristics of this type of system are not well understood, and partly for this reason, they are not commonly utilised. This paper reports on an experimental investigation into buoyancy-driven convection in a test rig designed to simulate the operation of a passive solar collector. The test rig comprised a vertical open-ended channel, approximately 1a square, heated from one side. The channel depth could be varied from 20mm to 110mm, and heating inputs varied from 200W to 1000W. Temperatures and airflow rates were measured and recorded, to characterise both steady-state and transient performance. The principal findings are: 1. Time constants (for heating)ranged typically between 30 and 70 minutes. 2. Flow regimes were mainly laminar (Reynolds number varing from ∼500 to ∼4000, depending on heat input and channel depth. 3. The thermal efficiency (as a solar collector and the heat transfer coefficient were functions of heat input, and were not depended on the channel depth. 4. The mass flow rate through the channel increased bath as the heat input increased and as the channel depth increased. The paper presents these findings and discusses their implications in more detail.(Author)
[en] PV-Trombe wall (PVTW) is a novel version of Trombe-wall. Photovoltaic cells on the cover glazing of the PVTW can convert solar radiation into electricity and heat simultaneously. A window on the south facade can also introduce solar heat into the room in the winter season. Experiment has been conducted to study the temperature field of a building with both southern facing window and the PVTW. A dynamic numerical model is developed for the simulation of the whole building system. The temperature of the indoor air is found to be vertically stratified from the measurement. The nodal model is adopted to calculate the temperature profile in the room. The simulation results are in good agreement with the experimental data. The different south facade designs affect the thermal efficiency of the PVTW significantly from the numerical simulation. With a southern facing window, the thermal efficiency of the PVTW is reduced by 27% relatively. The increase of PV coverage on the glazing can reduce the thermal efficiency of the TW by up to 17%. By taking account of electric conversion, the total efficiency of solar utilization is reduced by 5% at most while the glazing is fully covered with PV cells. The electric conversion efficiency of the PVTW achieves 11.6%, and is slightly affected by south facade designs.
[en] The paper presents the results of numerical investigations for determining the relationship between the replacement factor of heat load of passive solar heating passive systems and the thermal resistance of their collecting-accumulating walls. The calculations are carried out by using average daily meteorological information. (author)
[en] A thermal evaluation of a R-TW system (room with a Trombe wall) is presented. Hourly climatic data of the coldest and the warmest days of 2014 was used to assess the behavior of the R-TW in two cities of Mexico with cold climate (Huitzilac and Toluca). The simulations were done with an in-house code based on the Finite Volume Method. It was found that thermal energy losses through the semitransparent wall are about 60% of the solar radiation incident on the system (G_s_o_l). Despite of the thermal losses, the system gets enough energy to keep the air inside the room with a temperature above 35 °C. For both cities during the coldest day, the maximum energy stored is about 109 MJ and during the warmest day is about 70 MJ. This energy is supplied from the storage wall to the air inside the room during periods without insolation. - Highlights: • Thermal performance of a Room-Trombe Wall system was evaluated under two cold cities. • Thermal energy losses through the semitransparent wall were about 60% of the solar radiation incident of the system. • The maximum energy stored by the Trombe Wall was 109 MJ during the coldest day. • The maximum energy stored by the Trombe Wall was 70 MJ during the warmest day.
[en] Two types of phase change materials were used at storage media in a Trombe Wall , namely paraffin wax (N-Eicoseue C20H42) and Glauber's Salt (Na2So4.10H2O). To investigate the performance of these materials, a theoretical model and a simulation programme were developed. The wall temperature, the amount of heat stored, and the optimum wall thickness were calculated for both types. The study found that using two sheets of glass on the outside wall increased the surface wall temperature by around 50 degree centigrade. It also found that Glauber's salt was a much better storage materials than paraffin wax. For a selected winter day at a location of 32 deg. N latitude, the storage capacity of the salt was more than twice that of the paraffin wax. The salt storage capacity was 32816 kj/m3 at an optimum wall thickness of 16cm. This value for paraffin wax was 14464 kj/m3 at 13cm optimum thickness. The study also concluded that according to this high heating value the wall uses, Glauber's salt as a storage medium could supply its heat to the surrounding for a much longer period at night.(Author)
[en] The present work raises the use of solar energy as an aid for air conditioning by means of architectural envelope parts such as walls, basically as heat discharge systems. Using a thermal balance applied to these systems, an analytic model was formulated to simulate its behavior and to consider the time variation of the environmental temperature, solar radiation, heat storage in the wall and the temperature of the room to be ventilated. The analytical results were compared against experimental data, creating an experimentally validated model that gives confidence on the accuracy and trustworthiness of the analytic proposal. Six tests were carried out in the experimental model. In four of them, the heat flux simulation was performed with electrical resistors; in the other two, solar radiation was directly employed. The results show that the thermal performance of the system can be appropriately determined and described by the analytical model, within a small margin of error. The proposed analytic model can calculate the behavior of a heat discharge system in walls by simply knowing the dimensions of the prototype and the environmental conditions
[en] The installation in 1949 of the LES (solar energy laboratory) on Mont Louis-Odeillo in the Pyrenees, was emblematic of public commitment to passive solar power. Throughout the 1950's solar furnaces were supported for research into materials and solar powered homes, moving in phase with colonial policy. Then, with the construction at Odeillo of a giant solar furnace as part of the 'policy of grandeur', policy swung in the opposite direction. The study concludes with the role that the LES played at the time of the energy crisis in the 1970's and questions the French model of not developing solar energy