**5. Results and discussion**

From the graph of temperature (°C) versus time (min) as shown in **Figure 13**, an exponential decay curve was obtained. The graph was linear in the first 3 min and the thermoelectric air conditioner minimum temperature for that time was 22.3°C. For no heat load, the thermoelectric air conditioner was able to cool the enclosure to the desired thermal comfort temperature of 22°C in 6 min. A typical air conditioning system that operates on the refrigeration cycle takes approximately 30 min to cool a room to the thermal comfort temperature of 22°C [9, 10].


*Theoretical and Experimental Analysis of a Thermoelectric Air-conditioning System DOI: http://dx.doi.org/10.5772/intechopen.88664*

#### **Table 1.**

**4.2 Method/procedure**

**Figure 11.**

*Low-temperature Technologies*

**Figure 12.**

**70**

i. The thermoelectric air conditioning system was connected to the power

location of the thermocouples was noted as shown in **Figure 11**.

iii. The power strip was turned on which simultaneously powered on the

ii. The thermocouples were connected to the 12-Channel Thermometer and the

thermocouple data recorder and the thermoelectric air-conditioner as shown

From the graph of temperature (°C) versus time (min) as shown in **Figure 13**, an exponential decay curve was obtained. The graph was linear in the first 3 min and the thermoelectric air conditioner minimum temperature for that time was 22.3°C. For no heat load, the thermoelectric air conditioner was able to cool the enclosure to the desired thermal comfort temperature of 22°C in 6 min. A typical air conditioning system that operates on the refrigeration cycle takes approximately 30 min to cool a room to the thermal comfort temperature of 22°C [9, 10].

supply and connected to the power trip.

*Thermoelectric air conditioner placed inside of testing enclosure.*

*Testing enclosure showing points at which temperature were taken.*

in **Figure 12** and **Table 1**.

**5. Results and discussion**

*Temperature readings obtained from testing enclosure of thermoelectric air conditioner.*

**Figure 13.** *Graph of temperature/°C versus time/min.*

Therefore, the thermoelectric air conditioner has a much faster cooling rate as compared to the conventional air conditioning system. The thermometric device was able to cool the enclosure and maintain a minimum temperature of 26.5°C, however it was expected that the device would cool the enclosure much less than this temperature. This was limited to the high temperature on the hot side of the module. The temperature on the hot side of the thermometric module was stable at 39.6°C when the minimum temperature of the enclosure was 26.5°C. From the specification graph of the module, the temperature difference chosen was 30°C. Therefore, if the hot side of the module was maintained at a much lower temperature then the cold side of module would result in a lower temperature reading (**Tables 2** and **3**).

Cooling capacity of the unit,

*DOI: http://dx.doi.org/10.5772/intechopen.88664*

Coefficient of performance,

air conditioner.

conditioning system.

thermoelectric module.

**73**

*<sup>Q</sup>*\_ *cc* <sup>¼</sup> *<sup>m</sup>*\_*<sup>a</sup>* ð Þ *hi* � *ho*

*Theoretical and Experimental Analysis of a Thermoelectric Air-conditioning System*

<sup>¼</sup> <sup>0</sup>*:*<sup>008027</sup> kg

<sup>C</sup>*:*O*:*P*:* <sup>¼</sup> *<sup>Q</sup>*\_ *cc*

*Pin*

<sup>¼</sup> <sup>0</sup>*:*<sup>286</sup> 0*:*61511

¼ 0*:*465

In comparing the owning and operating costs of the thermoelectric air conditioner to an air conditioner that operates using the refrigeration cycle, the thermoelectric air conditioner was the better choice of approximately 47.5% cheaper in the overall costs. Although the overall cost of the thermoelectric air conditioner was cheaper, it consumes a considerable large amount of power of 695 W more. This resulted in a higher cost of electricity per year of \$156.12 more than the refrigeration

However, the major factors which influenced the thermoelectric air conditioner in being the overall cheaper choice are the; life span of the device and the operating costs. The thermoelectric air conditioner has a greater estimated life span of 7 years more than the refrigeration air conditioner. This is because the life span of the air conditioner that operates on the refrigeration cycle uses a compressor which is the "heart" of that air conditioning system, contains a lot of moving parts and is therefore more prone to failure. On the other hand, the thermoelectric air conditioner uses thermometric module which is the main component of the system, contains no moving parts. Maintenance of the thermometric air conditioner is also cheaper in which it does not need re-gassing or regular inspection check for gas leaks as compared to the refrigeration air

The coefficient of performance was calculated for the thermoelectric air conditioning system, which was found to be 0.465. This value is small in

racies in the experiment or heat leaks between the cold and hot side of the

comparison with the average coefficient of performance for the vapor refrigeration cycle of 3.0 [11, 12]. The main reason for this vast difference is the power consumption of the thermoelectric air conditioner. The experimental cooling capacity was found to be 286 W while the system was sized for 330 W. In comparison, this value showed a 13.1% reduction of cooling capacity which may be due to the power supply used to power the thermoelectric air conditioner, since the system was only consuming 615.11 W while it was calculated that the system needed 756 W in order to produce a cooling capacity of 330 W. Additional causes may be inaccu-

¼ 0*:*286 kW

¼ 286 W

s

� <sup>35</sup>*:*<sup>6</sup> kJ kg

Specific volume at inlet, *<sup>ϑ</sup>*<sup>1</sup> <sup>¼</sup> <sup>0</sup>*:*<sup>882</sup> <sup>m</sup><sup>3</sup> kg

15 CFM fan used = 0.00708 m3 s

$$\text{Mass flow rate, } m\_{\text{a}} = 0.00708 \frac{\text{m}^3}{\text{s}} \times \frac{1}{0.882 \frac{\text{m}^3}{\text{kg}}}$$

Mass flow rate, *m*<sup>a</sup> = 0.008027 kg s

Using a psychometric chart, the enthalpy was determined for both the inlet and outlet of the thermoelectric air conditioning unit.

Enthalpy of the air at the inlet, *hi* = 71.2 kJ kg Enthalpy of the air at the outlet, *ho* = 35.6 kJ kg Difference in enthalpy,

$$\begin{aligned} h\_d &= h\_i - h\_o \\\\ &= 71.2 \text{--} 35.6 \end{aligned}$$

$$= 35.6 \text{ kg}$$


**Table 2.**

*Voltage and current readings obtained from the multi-meter.*


#### **Table 3.**

*Experimental results of thermal properties of thermoelectric air-conditioner.*

*Theoretical and Experimental Analysis of a Thermoelectric Air-conditioning System DOI: http://dx.doi.org/10.5772/intechopen.88664*

Cooling capacity of the unit,

Therefore, the thermoelectric air conditioner has a much faster cooling rate as compared to the conventional air conditioning system. The thermometric device was able to cool the enclosure and maintain a minimum temperature of 26.5°C, however it was expected that the device would cool the enclosure much less than this temperature. This was limited to the high temperature on the hot side of the module. The temperature on the hot side of the thermometric module was stable at 39.6°C when the minimum temperature of the enclosure was 26.5°C. From the specification graph of the module, the temperature difference chosen was 30°C. Therefore, if the hot side of the module was maintained at a much lower temperature then the cold side of module would result in a lower temperature reading

kg

Using a psychometric chart, the enthalpy was determined for both the inlet and

kg

*hd* ¼ *hi* � *ho*

¼ 71*:*2–35*:*6

<sup>¼</sup> <sup>35</sup>*:*<sup>6</sup> kJ kg

**Thermoelectric module Voltage (V) Current (A) Power (W)** Module 1 11.85 18.11 214.60 Module 2 11.79 17.61 207.62 Module 3 11.96 17.32 207.15

**No. Inlet air temperature (°C) Outlet air temperature (°C) Power (W) Dry bulb Relative humidity % Dry bulb Relative humidity %** 1 30.7 60.6 17.1 52.1 614.25 2 28.1 60.9 18.8 54.2 617.10 3 31.5 59.7 16.9 54.8 613.98 Average 30.1 60.4 17.6 53.7 615.11

kg

<sup>s</sup> � <sup>1</sup> 0*:*882m3 kg

s

s

(**Tables 2** and **3**).

*Low-temperature Technologies*

Specific volume at inlet, *<sup>ϑ</sup>*<sup>1</sup> <sup>¼</sup> <sup>0</sup>*:*<sup>882</sup> <sup>m</sup><sup>3</sup>

outlet of the thermoelectric air conditioning unit. Enthalpy of the air at the inlet, *hi* = 71.2 kJ

Enthalpy of the air at the outlet, *ho* = 35.6 kJ

*Voltage and current readings obtained from the multi-meter.*

*Experimental results of thermal properties of thermoelectric air-conditioner.*

15 CFM fan used = 0.00708 m3

Mass flow rate, *m*<sup>a</sup> = 0.00708 <sup>m</sup><sup>3</sup>

Mass flow rate, *m*<sup>a</sup> = 0.008027 kg

Difference in enthalpy,

**Table 2.**

**Table 3.**

**72**

$$\begin{aligned} \dot{Q}\_{cc} &= \dot{m}\_a (h\_i - h\_o) \\ &= 0.008027 \,\frac{\text{kg}}{\text{s}} \times 35.6 \,\frac{\text{kJ}}{\text{kg}} \\ &= 0.286 \,\text{kW} \\ &= 286 \,\text{W} \end{aligned}$$

Coefficient of performance,

$$\begin{aligned} \text{C.O.P.} &= \frac{\dot{Q}\_{cc}}{P\_{in}} \\ &= \frac{0.286}{0.61511} \\ &= 0.465 \end{aligned}$$

In comparing the owning and operating costs of the thermoelectric air conditioner to an air conditioner that operates using the refrigeration cycle, the thermoelectric air conditioner was the better choice of approximately 47.5% cheaper in the overall costs. Although the overall cost of the thermoelectric air conditioner was cheaper, it consumes a considerable large amount of power of 695 W more. This resulted in a higher cost of electricity per year of \$156.12 more than the refrigeration air conditioner.

However, the major factors which influenced the thermoelectric air conditioner in being the overall cheaper choice are the; life span of the device and the operating costs. The thermoelectric air conditioner has a greater estimated life span of 7 years more than the refrigeration air conditioner. This is because the life span of the air conditioner that operates on the refrigeration cycle uses a compressor which is the "heart" of that air conditioning system, contains a lot of moving parts and is therefore more prone to failure. On the other hand, the thermoelectric air conditioner uses thermometric module which is the main component of the system, contains no moving parts. Maintenance of the thermometric air conditioner is also cheaper in which it does not need re-gassing or regular inspection check for gas leaks as compared to the refrigeration air conditioning system.

The coefficient of performance was calculated for the thermoelectric air conditioning system, which was found to be 0.465. This value is small in comparison with the average coefficient of performance for the vapor refrigeration cycle of 3.0 [11, 12]. The main reason for this vast difference is the power consumption of the thermoelectric air conditioner. The experimental cooling capacity was found to be 286 W while the system was sized for 330 W. In comparison, this value showed a 13.1% reduction of cooling capacity which may be due to the power supply used to power the thermoelectric air conditioner, since the system was only consuming 615.11 W while it was calculated that the system needed 756 W in order to produce a cooling capacity of 330 W. Additional causes may be inaccuracies in the experiment or heat leaks between the cold and hot side of the thermoelectric module.
