# A First Approach to Natural Thermoventilation of Residential Buildings through Ventilation Chimneys Supplied by Solar Ponds

^{*}

## Abstract

**:**

## 1. Introduction

## 2. Description of the Suggested Configuration

**Figure 1.**Functional diagram of the solar chimney supplied by the solar pond for the natural ventilation of residential buildings.

^{2}of the pond), due to the contribution of the radiant energy, which in the daytime the pond receives from the sun, it is possible to keep the pond at a constant temperature of during the whole season of use. This condition permits a constant temperature at the plate at the base of the chimney, regardless of outdoor climatic conditions [28], thus ensuring the ventilation of the building spaces.

## 3. The Computational Fluid-Dynamics Model

_{H}and T

_{C}are, respectively, the maximum and minimum temperatures of the system, and L is the characteristic dimension of the flow. If the collector height is taken as a characteristic dimension, the value of the Rayleigh number of the system examined is higher than the critical value Ra > 10

^{9}.

_{k}and G

_{b}are respectively the turbulent kinetic energy production caused by the mean velocity gradients and the floating forces.

- -
- Chimney walls and adiabatic hot plate covering;
- -
- Constant temperature of the hot plate;
- -
- Absence of wind velocity in correspondence of the chimney walls;
- -
- Pressure; temperature and intensity of the turbulence set to a certain distance both at the entrance of the hot plate and the exit of the chimney;
- -
- Conditions of the temperature and pressure in the assigned spaces.

Tp (°C) | Te (°C) | V_{chimney} (m/s) (at the Axis) | Err (%) | |
---|---|---|---|---|

C.B. Maya et al. [31] | Present Study [18,19] | |||

24.00 | 17.80 | 1.64 | 1.50 | −8.26 |

21.90 | 17.00 | 1.34 | 1.27 | −5.09 |

40.50 | 27.80 | 2.88 | 3.15 | −9.51 |

## 4. Results and Discussions

^{2}, due to the presence of solar radiation. In order to take into account the losses caused by the irreversibility of the exchangers and the necessary thermal difference between the pond and the exchanger, a constant temperature of the plate of 60 °C was assumed.

**Figure 4.**Trend of the air flows near the vents in the following floors (V

_{1}: vent at first floor; V

_{2}: vent at second floor) according to the temperature of the environment (T

_{e}) and the temperature of the plate (T

_{p}).

**Figure 5.**Trend of the total air flow near the chimney according to the temperature of the environment (T

_{e}) and the temperature of the plate (T

_{p}).

**Figure 6.**Trend of the air flows near the vents in the following floors (V

_{1}: first floor; V

_{2}: second floor) according to the temperature of the outdoor environment (T

_{e}) with a plate temperature of T

_{p}= 60 °C.

_{p}= 60 °C). It can be seen how vent 1 (first floor) is characterized by an air flow of 490 m

^{3}/h for an outdoor temperature of 18 °C and 840 m

^{3}/h for an outdoor temperature of 26 °C. The minimum value of the air flows in the first floor is higher than that present in the second floor. Considering the same outdoor air temperature differences, vent 2 (second floor) ensures a ventilation air flow that can vary from 350 to 620 m

^{3}/h. Therefore, even if the air flow presents minimum values in the floor considered less advantageous, if it is assumed for each vent a minimum air exchange of 0.3 vol/h (air exchange in conformity with the standards [32]), every vent can ensure an air exchange for those environments with a volume of about 1100 m

^{3}. When the outdoor temperature gets higher, the air flow increases with respect to the one necessary for the ventilation, thus representing a contribution to the free cooling of the environment with some savings regarding the energy consumption of the building and the thermal comfort of occupants of the indoor environment.

**Figure 7.**Trend of the heat power required by the plate (q) at the base of the chimney according to outdoor air temperature (T

_{e}).

^{2}, 30 W/m

^{2}, and 40 W/m

^{2}[20], the surface of the pond (Figure 8) necessary to provide the heat required ranges from 80 m

^{2}to 180 m

^{2}.

**Figure 8.**Necessary surface of the solar pond according to the minimum outdoor reference temperature (T

_{e}) and the heat collected per unit surface of the pond (q

_{ext}).

**Figure 9.**The zones painted and numbered furnish information about the feed and return diameter according to the ratio H/L: (1) feed diameter: 68 mm + return diameter: 62 mm; (2) feed diameter: 62 mm + return diameter: 51.5 mm; (3) feed diameter: 51.5 mm + return diameter: 39.7 mm; (4) feed diameter: 39.7 mm + return diameter: 35 mm; (5) feed diameter: 35 mm + return diameter: 26.5 mm.

## 5. Conclusions

## Acknowledgments

## Author Contributions

## Conflicts of Interest

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**MDPI and ACS Style**

Salata, F.; Alippi, C.; Tarsitano, A.; Golasi, I.; Coppi, M.
A First Approach to Natural Thermoventilation of Residential Buildings through Ventilation Chimneys Supplied by Solar Ponds. *Sustainability* **2015**, *7*, 9649-9663.
https://doi.org/10.3390/su7079649

**AMA Style**

Salata F, Alippi C, Tarsitano A, Golasi I, Coppi M.
A First Approach to Natural Thermoventilation of Residential Buildings through Ventilation Chimneys Supplied by Solar Ponds. *Sustainability*. 2015; 7(7):9649-9663.
https://doi.org/10.3390/su7079649

**Chicago/Turabian Style**

Salata, Ferdinando, Chiara Alippi, Anna Tarsitano, Iacopo Golasi, and Massimo Coppi.
2015. "A First Approach to Natural Thermoventilation of Residential Buildings through Ventilation Chimneys Supplied by Solar Ponds" *Sustainability* 7, no. 7: 9649-9663.
https://doi.org/10.3390/su7079649