Evaluation of decentralized ventilation system with heat recovery

Abstract

Humans spend 90% of their times indoors, and maintaining a pleasant indoor environment is essential. Factors like human behaviour, combustion sources, cleaning supplies, affect the indoor environment, which could potentially affect the human health.the most common answer to controlling the indoor environment is a good HVAC system. Ventilation systems with supply and exhaust are not standard in residential houses, natural ventilation with exhaust ducts or just mechanical exhaust system is conventional among the residential sectors. A cost-effective and an energy-efficient alternative could be a “Decentralized ventilation system” This report aims to provide knowledge of such innovation in the field of HVAC, to evaluate the performance of a decentralized ventilation window unit system.
The results aimed to declare the performance of a window unit decentralized ventilation system developed by SMARTVENT. The tests are done according to the standards that have to be followed, and the ventilation unit has performed up to those standards in various airflows. Nevertheless, it needs to be tested further to be released in the market. A separate control system must be built for this unit to do any further testings.

Popular Abstract

EVALUATION OF DECENTRALIZED VENTILATION UNIT with HEAT RECOVERY
Forty per cent of world energy use is in the building sector with an average increase of 3 % annually, in that 40 %, indoor comfort energy like space heating and cooling consume 30 % to 60 % based upon the region. The construction industry is moving towards the improvement of the indoor environment by reducing the energy consumption, by improving the insulation materials, windows and air-tightness and further on.
For indoor comfort, single dwellings are generally equipped with exhaust ventilation system or natural ventilation system together with district heating, and it is less common to see supply and exhaust mechanical ventilation systems. This could be due to factors like pipes and ducts passing all over the house, the usage of the equipment and the cost factors to install and maintain such a ventilation unit, which could be a concern for single-family housing.
To tackle this issue, one of the innovative idea was Decentralized ventilation system, which would not require as much space as a typical mechanical ventilation unit does.
This thesis project looked at evaluating of one such decentralized ventilation unit developed by SMARTVENT. The ventilation unit has two zones for supply air and exhaust air, with heat exchangers to the inside of the room and fans to push and pull air outside of the room. The ventilation unit works in two cycles. First, one zone supplies air into the room, and the second zone exhausts the air from the room. The zone cycles last for sixty seconds, and it takes further ten seconds to ramp up or down to change the rotation of the flow where the second cycle starts. In simple terms, in the first cycle, one zone takes air into the room, and in the next cycle, it takes the air out of the room.
To evaluate the ventilation unit, a series of tests were taken.
i. Airflow- This test determined the actual air flow from the equipment from 10.5 l/s being the highest 2 l/s being the lowest
ii. Air Draught- The sensation of sudden movement of air on exposed skin causes disturbances, upon testing with different airflows and at different points in the testing space. At three different heights of 0.6 m, 1.1 m, 1.7 m, at each point of the points marked all over the room. This test proved us that there is no presence of draft inside the room.
iii. Air leakage- it is a test to configure the airtightness of the room. The air change per hour calculated is later used to calculate, the actual air change per hour of the airflows from the equipment.
iv. Tracer gas- ACH is calculated in this method for five different airflows, 7 l/s, 10 l/s, 13l/s, 16 l/s, 19 l/s. Tracer gas decay method has been utilized, this test resulted in an explanation of airflow of 16 l/s and higher, can achieve the standards of at least 0.35 ACH in the residential sector.
v. Short-circuiting – when the air escapes the room as soon as it enters from the adjacent entry/exit port. This could be a severe issue in terms of performance of the ventilation unit, and it might not supply enough air into the room and extract enough air out. Using the tracer gas equipment it has resulted in knowing there is no issue of short-circuiting from the equipment.
vi. Temperature efficiency– last, and vital test to analyze the performance of the heat exchangers of the ventilation unit. The heat exchangers retain the heat more as the airflow decreases due to the air contacting more surface area of the exchangers. And the efficiency range from 66.5 % to 45 %.
A web application was utilized to control the ventilation unit, and the application was designed for previous ventilation unit. So the command from the web application and the ventilation unit for airflow does not match, and the unit performs 40 % to 60 % less. Considering this, the full potential of the ventilation unit is uncertain, and it requires future research to conclude.

• author: Chowdary, Sunkavalli Kowshik
• supervisor: Henrik Davidsson
• organization: Division of Energy and Building Design; Department of Architecture and Built Environment
• course: AEBM01 20201
• year: 2020
• type: M1 - University Diploma
• subject: Technology and Engineering
• keywords: Decentralized ventilation, airflow, air draught, heat exchangers, tracer gas
• language: English
• id: 9007503
• date added to LUP: 2020-04-09 12:25:37
• date last changed: 2020-04-09 12:25:37