An Integrated Passive Cooling System for Thermal Comfort

Abstract

In the hot and humid environment of Indian summers, a conventional cooling system is too expensive for most people. In this project, Passive cooling systems which consume less power, are more efficient, cost less, and make very little noise are used. After researching various passive cooling techniques in isolation and running simultaneously, we aim to develop a system that is cost-effective and efficient at cooling the Indian household. The focus of this project is on the four major types of passive cooling techniques, they are radiant cooling, solar chimneys, wind catchers, and shading devices. Supplementary techniques like terrace cooling are also included. The initial analysis and study of the windcatcher system with various heights and inlet shapes have been conducted. A software model has been generated using fusion 360, analyzed in Ansys fluent, and results were recorded. The radiant cooling system has been designed and an analysis of the system is done. Once the individual system analysis is successful, an integrated model containing all four systems will be generated and analyzed. The integrated system hence designed will ensure that there is cooling obtained in the room using low-energy passive cooling techniques.

Introduction

I. INTRODUCTION

India is a country with varied climates and a significant portion of the country is living in a hot and humid environment[1]. While many people long for relief from the scorching heat of the sun, an air conditioner is a luxury, that most can’t afford. In a developing country like India, the need for affordable cooling is becoming increasingly apparent. The project aims to provide an affordable cooling system that is accessible to a larger population than it was previously available to.

Conventional cooling has some disadvantages that can be improved with this project. It is costly to purchase and install. Requires frequent maintenance for optimal performance. It has many moving parts which lead to multiple points of failure and consume a massive amount of electricity.

These aspects of conventional cooling make it unsuitable for the majority of the population. However, passive cooling is different. Passive cooling systems consume less power, are more efficient, cost less, and make very little noise[2]. They are the ideal system for cooling in the Indian market. This project has the potential to be beneficial not just to any single individual but to the environment too.

It will benefit the common man by being cheaper than a conventional system and consuming less electricity at the same time. Since it consumes less electricity, it also reduces the fossil fuels burned to support the environmental impact of burning fossils. The HVAC industry is one of the largest consumers of electricity[3]. The project has the potential to reduce that consumption by a considerable margin.

The aim of this project is to analyze, design and fabricate a contained passive/hybrid cooling system.

1. To compare the statistical difference in performance between different passive cooling devices.
2. To evaluate the effectiveness of selected passive cooling devices..
3. To determine the rate of cooling in different passive cooling systems due to varied parameters.
4. To develop an optimal structure for a radiant cooling system.

II. METHODOLOGY

In this project, some research papers have been explored. Based on the research papers, the shortcomings and findings of research done on passive and hybrid cooling were analyzed. With the knowledge gained, a prototype will be fabricated based on the design finalized using software like SolidWorks, Ansys, etc. The final product will aim to compensate for some of the shortcomings noticed in previous research. The design will be for a residential apartment.

Simulations will be conducted on the finalized design of the model using Ansys having a fixed set

of parameters including orientation w.r.t. to the sun, ambient temperature and humidity, wind flow, and other factors.

III. DESIGN

In our design, we decided to incorporate the wind tower and radiant cooling system. A structure that was both performant, included the cooling mechanisms necessary and did not pose unnecessary challenges in the analysis stage was designed.

A. Wind Tower

And the dimensions of the radiant cooling system are:

• 3m height
• Modulated spiral
• Pipe length= 115 m
• Supply water temp= 9.6°C
• Velocity = 10.68 cm/s

D.   Human Figure Analysis

The analysis of the efficiency and performance of our cooling system would be incomplete without the presence of a heat source that would be present in the use case scenario of the system. Hence the team set out to design a human-shaped source of heat emission to complete our test scenario.

However, the designs were incapable of being meshed in the analysis stage. It was attempted using open-source externally available models but achieved little to no success. Hence it was decided to approximate the shape of a human body to a sphere (Fig 3.24) and adjust the parameters that affect heat output accordingly an were able to successfully proceed with the analysis.

The parameters used were as follows:

• Human shape:  Sphere
• Sphere Diameter = 780mm (for the average surface area of the adult human body)
• Sphere Location:  Arbitrary
• Heat transfer coefficient = 3.4 w/m2-k
• External emissivity = 0.96
• Heat generation rate = 2024.875 w/m3
• Body temperature: 36°C

These values correspond to an average human male’s statistic.

IV. RESULTS

Five separate analyses were conducted

A. Steady-state Comparison of x and k Blade Square Wind Catcher Performance

The physical dimensions used are identical for both wind catchers.

 In both scenarios, the outside air temperature was 23°C and the internal temperature was 31°C and an identical temperature drop of 8°C was obtained.

Conclusion

A. From the first analysis, it can be concluded that there is no statistical difference in performance between the x and k blade windcatcher for our experiment\'s climatic conditions, hence we can proceed with any design of windcatcher. B. From the second analysis, it can be concluded that the windcatcher mechanism is a viable method of cooling for our experiment’s location and climatic conditions with sizable cooling effects. C. From the third analysis it can be concluded that this cooling effect occurs in a short amount of time and attains equilibrium quickly. D. From the fourth analysis, an increase in wind catcher height increases the rate of cooling, and a temperature drop is noticed, but a definite relationship between the wind tower\'s height and cooling effect cannot be determined. E. From the fifth analysis it can be concluded that temperature drop and by extension cooling effect is directly proportional to wind tower height.

References

[1] Hindoliya, D. A., & Mullick, S. C. (2004). Direct Evaporative Cooling for Thermal Comfort in a Building in the Summer Months for Four Climatic Zones of India. SESI Journal, 14. [2] Dnyandip K. Bhamare, Manish K. Rathod, Jyotirmay Banerjee, Passive cooling techniques for building and their applicability in different climatic zones—The state of art, Energy and Buildings, Volume 198, 2019, Pages 467-490, ISSN 0378-7788. [3] Payne, F. William, and John J. McGowan. Energy management and control systems handbook. Springer Science & Business Media, 2012. [4] Chowdhury, Ashfaque & Rasul, Mohammad & Khan, M. Masud. (2008). Thermal-comfort analysis and simulation for various low-energy cooling-technologies applied 66 to an office building in a subtropical climate. Applied Energy.85.449-462. [5] American Society of Heating, Refrigerating and Air-conditioning Engineers. (2019). 2019 ASHRAE Handbook. Atlanta, Ga, American Society of Heating, Refrigerating and Air Conditioning Engineers. www.ashrae.org

Copyright

Copyright © 2022 Cleta Pereira, Ashley Dsouza, Clevon Dsouza, Anjishnu Datta, Ian Dsilva. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.