Conventional Trombe Wall Research Articles

Enhancing indoor thermal comfort and energy efficiency: A comparative study of RC-PCM Trombe wall performance

In response to the issue of excessive heating during summer in traditional Trombe walls, this study proposes a novel system called RC-PCM Trombe walls, which utilizes radiation cooling and phase change materials (PCMs) to traditional Trombe walls. The thermal performances of RC-PCM Trombe wall, conventional Trombe wall, and PCM Trombe wall were compared and studied under summer conditions. The experimental results demonstrate that the addition of heat pipes and radiant cooling devices to the RC-PCM Trombe wall led to a reduction of peak temperatures on the inner surface of the south wall by 3 °C and 1.2 °C, respectively. Furthermore, the time taken to reach the peak temperature was delayed by 43 min and 38 min, respectively. The standard deviations of indoor air temperature were reduced by 0.04 °C and 0.29 °C, while the indoor heat gain was reduced by 26.5 % and 55.2 %, respectively. These findings indicate that the RC-PCM Trombe wall effectively mitigates indoor overheating and enhances the indoor thermal environment during the summer.

Experimental studies on the energy performance of a novel wavy-shape Trombe wall

Trombe wall is widely used as a passive solar technique to reduce energy consumption in buildings. Numerous studies have been carried out on improving the conventional Trombe wall, but few of them have focused on the impact of its shape on energy performance. In this research, the energy performance of the novel wavy-shape Trombe wall has been investigated. The experimental results showed that the novel wavy-shape Trombe wall model with an intersection angle of 90° or 120° has significantly improved the air velocity, surface and airflow temperatures, resulting in better overall performance. The heat flux of the wavy-shape Trombe wall model with an intersection angle of 90° is 24% and 68% higher than that of the flat model with the incidence angles of 40° and 60° respectively. The heat flux of the wavy-shape Trombe wall model with an intersection angle of 120° is 7%, 8%, and 4% higher than that of the flat model with the incidence angles of 20°, 40°, and 60° respectively. The results showed that a wavy-shape Trombe wall with a proper intersection angle, within a considerable percentage of daytime, has a much better energy performance than a traditional Trombe wall.

The impacts of advanced glazing units on annual performance of the Trombe wall systems in cold climates

Building envelopes play substantial role in maintaining the thermal comfort, and reduction of the energy demands in buildings, and Trombe walls are among the most efficient passive solutions for application in envelopes. Taking into account the rareness, limitations and shortcomings of the studies on glazing units of the Trombe walls and the advances in glazing technologies of the buildings, in this study physical and thermal properties of the utilized glazing units with advanced technologies and innovative configurations were investigated with focus on maintaining the highly passive functionality of the Trombe walls. Moreover, contrary to the largest extent of the former studies, the performances of the configurations in cold climates were studied annually with detailed focus on thermal requirements on different periods. Thus, wide ranges of numerical models were developed with validated methods and approaches. In this regard, novel Trombe walls with various window-to-wall ratios have been evaluated, and the impacts of different structural and spectral specifications are studied which is unprecedented. The annual heating, cooling, overheating, and comfort periods have been assessed distinctively, and solutions for boosting the efficiency of the prevalent Trombe walls through improving the specifications of the glazing units are presented. It was found that the application of Trombe walls with advanced glazing units leads to reduction of the heating period (48.8%), and improvement of the comfort conditions (23.9%), however it increases the cooling (22.7%) and overheating (2.2%) periods averagely. The physical properties (reduction ofwindow-to-wall ratios) is the most effective on improvement of comfort conditions (32%), and cooling periods (35%), however the structural properties of the glazing units are the most influential on reduction of the overheating periods (up to 12.2%). This study proves the undesirable performance of the conventional Trombe wall assemblies (window-to-wall ratio of 99%) by considering the annual assessments rather than focusing on heating period.

Numerical and experimental study on the performance of a Photovoltaic Trombe wall system with Venetian blinds

The integration of a photovoltaic system with the Trombe wall system (PVTW) is effective in thermal load regulation of buildings and electrical energy production. The modification of the PVTW system by adding a Venetian blind can regulate the airflow and provide shading. In this study, the experimental and numerical simulation results for the novel Photovoltaic Trombe wall system with a Venetian blind (PVTW_Ven) and the conventional Trombe wall system with a Venetian blind (TW_Ven) are compared. The experiments were conducted in a test room equipped with the PVTW_Ven and TW_Ven systems located in Abha, Asir Province of Saudi Arabia, with semiarid climatic conditions. The results obtained by numerical simulation were validated by comparing with experimental results. The results indicate that the average heat gain of the TW_Ven configuration is 1.33 times more than that of the PVTW_Ven configuration, with a 5.2 °C higher outer wall surface temperature. The temperature can be systematically regulated inside the test room by installing a Venetian blind with the slats at optimal 60° in the air gap of both configurations. The maximum temperature of the Venetian blind in the PVTW_Ven configuration is 4.7 °C lower than that in TW_Ven.

Enhancement of natural convection for improvement of Trombe wall performance. An experimental study

This experimental work shows that the natural convective heat transfer in the active enclosure of a conventional Trombe wall assembly is enhanced by the interposition of transparent and vertical partitions. Quantification of the average Nusselt number corresponding to both versions with and without partitions was carried out by means of a 1/5 scale assembly. The glass cover is maintained isothermal at cold temperature while the active wall generates a variable heat flux simulating the incident solar radiation. The distance between the two active and parallel walls is variable. Four ratios between this distance and the height of the wall are considered, associated with a wide range of Rayleigh number reaching 4.1 × 109. An error calculation is carried out for all the processed configurations, taking into account the experimental uncertainties of the measured physical parameters. The maximum error found on the average Nusselt number is low, of about 5%. Measurements made by means of an interstitial medium without partitions are consistent with the results of other work carried out by experimental and numerical approaches in specific ranges of Rayleigh number. This study reveals the partitions effectiveness, since the natural convective heat transfer's increase lies between 10.0% and 14.4% according to the considered configuration. Correlations are proposed in the present work in order to calculate the average natural convective Nusselt number for the conventional Trombe wall without partitions and for its improved version, for any aspect ratio and in the whole range of the considered Rayleigh number. They contribute to the optimization of the thermal design of this interesting assembly.

Study on a high-performance photocatalytic-Trombe wall system for space heating and air purification

This article proposes a novel solar gradient-utilization photocatalytic-Trombe wall system that can realize the dual functions of space heating and removal of indoor formaldehyde. A photocatalytic layer is coated on the internal surface of the glazing cover in conventional Trombe wall system. Under solar radiation, ultraviolet light is absorbed by the photocatalytic layer to activate the photocatalytic oxidation of formaldehyde, and the rest of visible and infrared parts are collected by the absorber plate to heat indoor environment. In this article, firstly, an experimental testing set-up of photocatalytic-Trombe wall was constructed and a full-day experiment was conducted to investigate the performances of air heating and formaldehyde degradation. Secondly, a coupled kinetic, thermal and mass model was derived and verified by the experimental data. Finally, adopting the established model, the seasonal energy saving analysis and economic analysis in Hefei were conducted. Results are: (1) Based on the experimental results, the daily air heating efficiency was 0.351, and daily generated clean air and degradation mass of formaldehyde were 164.0 m3/(m2 day) and 100.0 mg/(m2 day), respectively; (2) Experimental results confirmed the model accuracy within 8%; (3) Compared with the total thermal load reduction of 246.9 MJ/m2 in heating seasons for conventional Trombe wall, photocatalytic-Trombe wall not only has a higher value of 309.9 MJ/m2, but also an additional valuable total generated clean air of 4764.9 m3/m2; (4) Photocatalytic-Trombe wall system takes about 12.1 years to recoup the initial investment only considering the saving electrical by indoor space heating.

The performance analysis of a novel TC-Trombe wall system in heating seasons

Thermal-catalytic-Trombe (TC-Trombe) wall system can simultaneously realize the dual functions of space heating and air purification without added energy. Adopting the established coupled kinetic, thermal and mass model of TC-Trombe wall system, in terms of the seasonal performance of space heating and formaldehyde degradation in heating seasons in Hefei, the effect of the thermal storage by the massive wall and the comparisons with conventional Trombe wall system are investigated. The results indicate to some degree, the thermal storage by the massive wall decreases the performance of formaldehyde degradation and space heating for TC-Trombe wall system. Compared with the performance of conventional Trombe wall system, although existing the reduction of 28.3% in terms of the total thermal load reduction for TC-Trombe wall system, this combined system can constantly produce the total volume of clean air of 8328.7 m3/m2. Based on the analytical results, TC-Trombe wall with the sandwich structure is proposed. And the calculation results show that with the adding of the sandwich structure in TC-Trombe wall system, the total volume of clean air and total thermal load reduction increases by 20.9% and 34.9%, respectively. And TC-Trombe wall with the sandwich structure obtains the total volume of clean air of 10068.4 m3/m2 and total thermal load reduction of 270.6 MJ/m2 when the thermal insulation layer thickness is 20 mm. Therefore, TC-Trombe wall with the sandwich structure provides an efficient energy-saving strategy for obtaining a healthy and comfortable indoor environment using the solar energy.

A novel design of solar chimney for cooling load reduction and other applications in buildings

Cooling load accounts for more than 70% of the electric energy used in buildings in the Middle East. This paper presents a passive method to reduce the cooling load in buildings. The proposed concept includes adding an external solar shield enclosing an air gap between it and the outer wall of the building. This external solar shield layer would absorb the solar radiation incident on the outer walls of the building and get heated inducing a convective airflow in the gap between the layer and the building. This is an example of solar chimney in a flat geometry with a superficial resemblance to Trombe wall. Conventional Trombe wall channel heats the building external wall and creates a convective flow in-between a transparent glass layer and the heated wall. This hot flow is used either as a warm inlet air to the building in winter or help inducing airflow from inside the building for ventilation in summer. However, in the present work, the solar chimney induced airflow is purely external to the building.The proposed external solar shield starts with a glass layer from outside followed by an opaque porous metallic layer followed by an air channel before the building outer walls. The absorbing porous layer would get heated up quickly and transfer its heat to the air in the gap effectively due to its large surface area. The porous layer thickness is optimized at 15cm while the air gap is optimized at 0.3m. Numerical simulations based on finite volume analysis using ANSYS Fluent were carried out for a wall of 3m height. Comparisons of the performance of buildings with its outer walls shielded by white painted, black painted and glazed walls are presented and discussed with respect to that of buildings with bared outer walls as a control.Putting glazing alone after an air gap, expectedly, increases the heat gained by 47–56% compared to 0.7 emissivity simple bared wall. Single black and white solar shielding walls reduce the heat gain by 30 and 67%, respectively. However, the proposed design of a solar chimney with a glass outer wall followed by a porous foam metal layer on its inner surface, reduced thermal gain by 67–79%. This results in electrical cooling load reduction by about 28%. Furthermore, the heated airflow induced by a solar chimney formed with a 20×3m south wall can be utilized to induce water evaporation of 625–1046kg/day allowing active evaporative cooling and/or water desalination under solar irradiation condition of Dhahran, Saudi Arabia

An innovative Trombe wall as a passive heating system for a building in Athens—A comparison with the conventional Trombe wall and the insulated wall

Solar energy utilization for covering the heating loads of buildings is an innovative and clean way which leads to lower electricity consumption. Passive heating systems are low-cost and simple technologies which are able to cover a great part of the space heating demand. Trombe wall is the most mature technology for capturing solar irradiation and transferring it inside the building in order to cover a part of the heating loads, especially the hours after the noon. In this study, an innovative Trombe wall with an extra window in the massive wall is suggested. This wall is compared with the conventional Trombe wall and the usual insulated wall in order to make a complete investigation. The examined walls are located in south direction, in order to maximize the impact of solar irradiation. According to the final results, the new Trombe wall is the most appropriate technology, creating warmer indoor profile than the other cases, especially the hours between noon and afternoon. The analysis in performed with the commercial software Solidworks Flow Simulation and the examined building is located in Athens, Greece.

Heat transfer and air movement in the ventilated air gap of passive solar heating systems with regulation of the heat supply

The article describes the heat transfer and air movement that occur in the ventilated air gap of a building's passive solar heating system under winter and summer conditions. The physical and mathematical models of these processes are presented for the Trombe wall with and without venetian blinds arranged in the air gap. The mathematical models allow for the determination of the heat and air stream distribution and the surface temperature change of the constructive elements in both cases. The transfer of heat by radiation and convection are considered separately, making it possible to estimate in an analytical way the influence of constructive materials and covering properties on the heat flow distribution and regulate it.The mathematical models were developed on the basis of the analysis of the heat transfer and air movement and therefore they can be complemented and improved depending on the constructive and climatic conditions. Examples of comparative calculations of the heat transfer and air movement in the air gap of the conventional Trombe wall and the Trombe wall equipped with a venetian blind for regulation of heat supply are presented. For the winter period the comparative calculations were carried out with a different intensity of solar radiation.

Modelling free convection in a trombe wall

In this paper, the convective laminar heat transfer between the channel surfaces of the Trombe wall and a modified version of the conventional Trombe wall have been investigated. Velocity profiles, temperature profiles, and pressure defect have been investigated for the conventional Trombe wall, when the temperature of the masonry wall is not uniform but of the form T w ( x) = T g + Ax n . The variation of fluid velocity, temperature and the average Nusselt number have been determined numerically for selected tilt angles of the glass wall for the modified version of the Trombe wall. It was found that there is a significant effect of the glass wall inclination on the average Nusselt number.