Performance and flow characteristics of floor swirl diffuser under differ

International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –

6340(Print), ISSN 0976 – 6359(Online) Volume 4, Issue 4, July - August (2013) © IAEME

154

PERFORMANCE AND FLOW CHARACTERISTICS OF FLOOR SWIRL

DIFFUSER UNDER DIFFERENT OPERATING AND FLOW PARAMETERS

1Suraj,

2Dr. V.N. Bartaria

1

Suraj, ME Scholar, LNCT, Bhopal 2Dr. V.N. Bartaria, Prof. & Head, LNCT, Bhopal

ABSTRACT

Floor swirl diffusers used in air-conditioning system can create better air mixing to enhance

indoor air quality and help in achieving better human comfort. The variation in temperature in air

conditioning system depends strongly on the flow characteristics produced by the diffuser outlet that

vary considerably between different modeling set ups. In corporate sector it is very important to

calculate the effect of variation in temperature of diffused air from floor swirl diffuser with and

without heat load.

In this experimental work, I have tried to reduce the variation in temperature of conditioned

air and improvement in thermal human comfort by adopting different models of floor swirl diffuser

designed on pro-E software. After that I have made prototype wooden model of the floor swirl

diffuser to check its performance under different operating and flow conditions experimentally.

The experiment has been performed inside an acrylic sheet wooden room of size 4ft x 4ft x

5ft with floor swirl diffuser models installed at the roof. The variation in temperature of diffused air

form floor swirl diffuser at different altitude and the effect of heat load on temperature variation is

determined. This experiment has been performed on three different models of floor swirl diffuser

having different slot angles of 7⁰, 8⁰ and 9⁰.

Keywords: ACE-Air Change Effectiveness, Heat Load Capacity, Swirl motion, 7⁰ Swirl Diffuser-

Diffuser having slot with draft angle 7⁰, 8⁰ Swirl Diffuser- Diffuser having slot with draft angle 8⁰,

9⁰ Swirl Diffuser- Diffuser having slot with draft angle 9⁰,and Round and rectangular slots, Cross-

section.

INTERNATIONAL JOURNAL OF MECHANICAL ENGINEERING

AND TECHNOLOGY (IJMET)

ISSN 0976 – 6340 (Print)

ISSN 0976 – 6359 (Online)

Volume 4, Issue 4, July - August (2013), pp. 154-165 © IAEME: www.iaeme.com/ijmet.asp Journal Impact Factor (2013): 5.7731 (Calculated by GISI) www.jifactor.com

IJMET

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155

INTRODUCTION

Floor air diffusers are used widely in air-conditioning systems for distribution of conditioned

air inside a room and the air diffusion is very much depends on the characteristics of different

diffuser designs. For floor-level air supply systems, swirling diffusers are most widely used.

Modeling of the diffuser plays an important role in predicting airflow pattern in the room. Swirl

diffusers are generally mounted into the underfloor air handling space. This device delivers

conditioned air at floor level to the space and allows the occupant to manually control both the

volume and direction of the air flow. The diffuser is constructed of a durable, high impact,

polycarbonate material. Delivering air from the floor has an advantage of supplying fresh, cool, clean

air directly into the occupied zone of the space, so heat and pollutants are not continuously circulated

within the space as it happens in an overhead air distribution system. It will results in dissipation of

heat and less concentration of pollutants in the occupied space in the lower level than those at the

upper levels of the space. Ventilation is done through displacement as opposed to dilution.

The requirement of a good air distribution system is to supply clean and fresh air with less

variation in temperature with height and different locations to provide thermal comfort and high air

quality. In Asian and European countries, 30-50% of occupants have health problem because of bad

air distribution system. Almost 30-40% of the energy produced has been spent on air distribution

system in most of the developing countries.

Swirl diffusers are designed to provide effective indoor air diffusion through specially

designed swirl deflection blades to produce a highly turbulent radial air flow pattern that will induce

better mixing of room air. This also results in rapid temperature equalization to give stable room

conditions with minimum temperature gradients. The excellent high qualities of air from swirl

diffusers enable designers to aim for a high value of Air Change Effectiveness (ACE). Swirl

diffusers have recently become very popular because they generate radially high induction swirl air

flow by drawing room air up into the supply air pattern to induce superior air mixing. Better mixing

means better ACE.

It is therefore required to study the characteristics of air distribution system with floor swirl diffuser

under different operating and flow conditions with high thermal load.

EXPERIMENTAL SET-UP

It consists of an acrylic sheet wooden room of size 4ft x 4ft x 5ft with different models of

swirl diffuser installed at the floor level. The conditioned air from air conditioner is supplied from

the bottom through a duct of reducing cross-section to increase the air flow velocity through the

diffuser. A heater of 1500W is placed inside the room to provide a heat load. Heater is placed near

the location Y2. A temperature sensing instrument with six thermocouple wires is placed inside the

room to measure the temperature at six locations vertically at a distance of 0.7 feet. There are four

exhaust vents at the top surface of the wooden block through which ventilation is carried out inside

the room.

There are six locations at the floor inside the room where readings of temperature have to be

noted and the variation in temperature of air is to be studied.

3-D view of the experimental set-up and actual front view of the experimental set-up is

shown in Fig.1 and Fig.2 respectively.



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Fig.1 3-D view of the experimental set-up

Fig.2 Front view of the experimental set-up

DIFFERENT MODELS OF DIFFUSER

1. 7⁰ Swirl Diffuser

It has a circular cross-section of 280mm diameter and height 280mm. Round slots are cut on

the top surface. Round slots are drafted through an angle of 7⁰ for producing swirl action. Width of

the top surface is 10mm. Vertical surface of the diffuser is cylindrical with rectangular slots of size

10mm x 200 mm are cut on its surface.

Fig.3 Top view of 7⁰ Swirl Diffuser Fig.4 Front view of 7⁰ Swirl Diffuser



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FLOW PATTERN OF AIR THROUGH DIFFERENT DIFFUSER

The flow pattern of air through different diffusers can be visualized with the help of smoke.

The smoke is created inside the diffuser chamber and it is accelerated through the diffuser by the

conditioned air coming from the air- conditioner.



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Fig.9 Air flow pattern through 7⁰ Fig.10 Air flow pattern through 8⁰

Swirl Diffuser Swirl Diffuser

Fig.11 Air flow pattern through 9⁰ Swirl Diffuser

EXPERIMENTAL RESULTS

The main results of the experiment are tabulated at six locations inside the room with and

without heat load. Locations are taken along X-axis and Y-axis on the floor. These locations are

equally spaced and are at a distance of 1 foot from each other.

The supply air temperature from the air-conditioner is 18.4⁰C at a flow rate of 0.2m3/s. The

heat load is applied inside the room with the help of heater of load capacity 1500W.

Various temperature readings are noted at location Y1, Y2, Y3, X1, X2 and X3 with load and

without load. The experiment has been performed with all three models of diffuser.

These experimental results will help us in comparing the performance of three different

models of floor swirl diffuser under different operating and flow conditions. These results have been

plotted graphically between temperature and height from the floor level. It will also provide the

designers a guideline in achieving better human comfort and best performance with floor swirl

diffuser used in air conditioning system.

The graphs plotted between temperature and height at various locations indicates that

variation in temperature with height is less with 8⁰ swirl diffuser. The result also shows that variation

in temperature reduces as we move away from the heat source. Due to swirl action produced by the



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diffuser temperature equalization is almost achieved inside the room at different locations with and

without heat load. During the experiment performance only one exhaust vent is opened out of the

four. We can also perform the same experiment with all the four vents are opened.

The variation in temperature at location Y1, Y2 and Y3 is comparatively more than at

location X1, X2 and X3 during presence of heat load. This happens due to presence of heat source at

location Y2.

AIR TEMPERATURE MEASUREMENT

Air temperature is measured spontaneously at each location under different operating

conditions. Inlet and return air temperature are 18.4⁰C and 23.6⁰C for 7⁰ swirl diffuser, 18.4⁰C and

22.4⁰C for 8⁰ swirl diffuser and 18.4⁰C and 23.8⁰C in case of 9⁰ swirl diffuser respectively.

A uniform temperature distribution is observed. The highest temperature gradient is found at location

Y2. In the upper occupied zone there is small temperature gradient due to good mixing of air in the

upper region.

The temperature at various locations is tabulated and the graphical results are shown below.

Condition1: When exhaust vent 1 is opened

Initial Room Temperature= 32⁰C

Room Temperature at load 1500W without switching air-conditioner= 38⁰C

At location Y1

Load= No load with a.c.

S. No. Height (ft.) Temperature (⁰⁰⁰⁰C)

7⁰⁰⁰⁰ 8⁰⁰⁰⁰ 9⁰⁰⁰⁰

1 0.7 24 23 25

2 1.4 24 23 23

3 2.1 23 21 21

4 2.8 24 22 23

5 3.5 23 21 24

6 4.2 22 20 22

At location Y1 Load= 1500W load with a.c.

S. No. Height (ft.) Temperature (⁰⁰⁰⁰C )

7⁰⁰⁰⁰ 8⁰⁰⁰⁰ 9⁰⁰⁰⁰

1 0.7 26 25 24

2 1.4 25 25 23

3 2.1 25 24 23

4 2.8 25 25 25

5 3.5 23 25 25

6 4.2 22 22 23



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At location Y2 Load= No load with a.c.


7⁰⁰⁰⁰ 8⁰⁰⁰⁰ 9⁰⁰⁰⁰

1 0.7 26 24 26

2 1.4 24 23 23

3 2.1 23 22 22

4 2.8 24 23 24

5 3.5 23 22 24

6 4.2 21 21 22

At location Y2

Load= 1500W load with a.c.


7⁰⁰⁰⁰ 8⁰⁰⁰⁰ 9⁰⁰⁰⁰

1 0.7 30 28 31

2 1.4 28 28 29

3 2.1 26 26 25

4 2.8 25 26 26

5 3.5 24 25 25

6 4.2 22 22 22

At location Y3 Load= No load with a.c.


7⁰⁰⁰⁰ 8⁰⁰⁰⁰ 9⁰⁰⁰⁰

1 0.7 24 23 26

2 1.4 23 23 22

3 2.1 22 22 20

4 2.8 23 23 23

5 3.5 23 23 23

6 4.2 21 22 21

At location Y3

Load= 1500W load with a.c.


7⁰⁰⁰⁰ 8⁰⁰⁰⁰ 9⁰⁰⁰⁰

1 0.7 30 25 28

2 1.4 28 26 26

3 2.1 26 23 24

4 2.8 26 25 25

5 3.5 25 25 25

6 4.2 23 22 22



161

At location X1 Load= No load with a.c.


7⁰⁰⁰⁰ 8⁰⁰⁰⁰ 9⁰⁰⁰⁰

1 0.7 24 23 27

2 1.4 24 23 23

3 2.1 22 22 20

4 2.8 23 23 24

5 3.5 22 23 23

6 4.2 21 21 22

At location X1 Load= 1500W load with a.c.


7⁰⁰⁰⁰ 8⁰⁰⁰⁰ 9⁰⁰⁰⁰

1 0.7 25 24 25

2 1.4 23 24 23

3 2.1 23 22 23

4 2.8 25 25 25

5 3.5 24 24 24

6 4.2 22 21 21



7⁰⁰⁰⁰ 8⁰⁰⁰⁰ 9⁰⁰⁰⁰

1 0.7 24 23 26

2 1.4 22 23 22

3 2.1 21 22 20

4 2.8 23 22 24

5 3.5 22 22 24

6 4.2 19 20 21



7⁰⁰⁰⁰ 8⁰⁰⁰⁰ 9⁰⁰⁰⁰

1 0.7 24 25 25

2 1.4 23 25 23

3 2.1 22 23 23

4 2.8 23 25 24

5 3.5 22 24 24

6 4.2 20 21 21



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7⁰⁰⁰⁰ 8⁰⁰⁰⁰ 9⁰⁰⁰⁰

1 0.7 24 22 24

2 1.4 22 22 23

3 2.1 22 21 22

4 2.8 22 21 24

5 3.5 23 22 24

6 4.2 21 21 22



7⁰⁰⁰⁰ 8⁰⁰⁰⁰ 9⁰⁰⁰⁰

1 0.7 24 24 24

2 1.4 24 24 23

3 2.1 23 24 23

4 2.8 23 23 24

5 3.5 24 24 24

6 4.2 22 23 23

GRAPHICAL REPRESENTATION OF RESULTS

The following graph shows the variation in temperature with height at different locations in

experimental set-up.

Fig.12 Variation in temperature vs. height at Fig.13 Variation in temperature vs. height at

location Y1 in condition 1 without load location Y1 in condition 1 with load 1500W



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Fig.18 Variation in temperature vs. height Fig.19 Variation in temperature vs. height at

at location X1 in condition 1 without load location X1 in condition 1 with load 1500W



164

Fig.20 Variation in temp. vs. height at Fig.21 Variation in temperature vs. height at

location X2 in condition 1 without load location X2 in condition 1 with load 1500W

Fig.22 Variation in temp. vs. height at Fig.23 Variation in temperature vs. height at

location X3 in condition 1 without load location X3 in condition 1 with load 1500W

CONCLUSIONS

The results from this study show that a workshop with floor-supply displacement ventilation

using swirl diffuser can improve indoor air quality because the contaminant concentration in the

breathing zone is lower than that of mixing system. It helps us in comparing the performance of three

different types of swirl diffuser under different operating and flow conditions. Due to swirl action

produced more unidirectional flow was created, the slow recirculation at the occupant zone was

eliminated for the floor-supply ventilation and the risk of cross contamination can be effectively

reduced. The system with the swirl diffusers can provide a better comfort level than that with the

perforated panels due to the mixing by the diffusers.

This study helps in selecting optimum models for floor swirl diffuser under different

operating conditions. We can improve the Air Change Effectiveness and human comfort by varying

the slot design angle of diffuser. It will results in better mixing of air inside the room and the

variation in temperature of air from floor height will be reduced. We can achieve better human

comfort and proper ventilation by using floor swirl diffuser.



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Performance and flow characteristics of floor swirl diffuser under differ

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