In this study, the inlet and outlet air exhaust temperatures from chimney, the inlet and outlet water temperature from water reservoir, and thermal efficiency of the waste heat recovery application. The experimental study was used to assess the performance of the waste heat recovery application using pulsating heat pipe to produce hot water. Furthermore, cost of one cubic meter of hot water generation (CPH), and environmental analysis of waste heat recovery system are presented and discussed. The different angles of the pulsating heat pipe was tested to optimized best angle of heat pipe. Each experiment is done four times to reduce the errors. With respect to the annual measuring of energy produce and hot water, the data of the one-day experiment (December 2, 2020) were applied to all days of the year. Fig. 6 shows the inlet and outlet temperature of the air exhaust from chimney. The outcomes revealed that the lowest temperature of outlet air temperature from channel was obtained at angle of 90 degrees, which was equal to 105.1 oC. Also, the amount of inlet air temperature in channel was the same at different and was equal to 180 oC. Moreover, the angle of the pulsating heat pipe has an inverse effect to air outlet temperature of channel due to increasing the heat transfer rate between air exhaust and water reservoir.
Figure 7 depicts the temperature of inlet and outlet water of the hot water reservoir. The results showed that the maximum hot water temperature in outlet of reservoir was achieved at angle of 90 degrees, which was about to 58 oC. Also, the amount of inlet water temperature in reservoir was about 33 oC. Moreover, the angle of the pulsating heat pipe has a direct impact to hot water outlet temperature of reservoir due to enhance in heat transfer rate between an air exhaust and water reservoir.
Figure 8 indicates the energy efficiency and pulsating heat pipe temperature of the waste heat recovery system. As observed, the highest energy efficiency and pulsating heat pipe temperature was achieved in angle of 90 degrees, which were equal to 54% and 80 oC, respectively. By increasing the evaporator surface temperature of PHP, the thermal efficiency of the application increased due to increasing the heat transfer between water and heat pipes. Also, the lowest energy efficiency was about 19% which was occurred in angle of 0 degrees.
Figure 9 illustrates the energies of hot water, air exhaust and waste heat energy from the system. The obtained outcomes showed that as the energy of hot water raised, the energy of air exhaust decreasing due to high heat transfer between heat pipes and water. The highest energy of hot water was equal to 872 W which was occurred in angle of 90 degrees. Also, the waste heat energy of the system was increased by increasing the angle of the PHP. The highest waste heat energy of the system was occurred in angle of 0 degree, which was about 1303 W.
Table 2 provides the price of fabrication of the waste heat recovery system. The results revealed that the price of fabrication and salvage value of the waste heat recovery system are about 117$ and 23.4$, respectively. Table 3 depicts the price of one cubic meter of hot water production with using waste heat recovery system. The results indicated that the annual hot water generation and CPH of the system were equal to 262.8 m3/year and 0.1 $/m3, respectively.
Table 2
Cost of fabricated of waste heat recovery application using pulsating heat pipe
Waste heat recovery system` components | Cost of system ($) | Salvage value ($) |
Galvanized body of channel | 35 | 7 |
Pipes of air exhaust | 10 | 2 |
Galvanized support | 12 | 2 |
Pulsating heat pipe | 30 | 6 |
Water reservoir | 20 | 4 |
Aluminum sheet | 10 | 2 |
Total cost | 117 | 23.4 |
Table 3
Economic analysis of waste heat recovery system
Type | n (year) | i (%) | CRF | FAC ($/year) | SFF | S ($) | ASV ($/year) | AMC ($/year) | UAP ($/year) | M (m3/year) | CPH ($/m3) |
Waste heat recovery | 20 | 0.2 | 0.205 | 24.03 | 0.005 | 23.4 | 0.125 | 2.4 | 26.3 | 262.8 | 0.10 |
Table 4 presents the embodied energy to generate various goods and material used in the application using PHP for generate hot water. The embodied energy of the waste heat recovery system was about 439.7 kWh.
Table 4
Embodied energy of different material of waste heat recovery application
Type | Name of material | Energy density | Weight of component (kg) | \(\text{E}\text{m}\text{b}\text{o}\text{d}\text{i}\text{e}\text{d} \text{e}\text{n}\text{e}\text{r}\text{g}\text{y}\) (kWh) |
MJ/kg | kWh/kg |
Waste heat recovery system | | | | | |
| Aluminum sheet | 199 | 55.2 | 1.3 | 71.8 |
| Galvanized body of channel | 50 | 13.9 | 3.5 | 48.6 |
| Galvanized body of reservoir | 50 | 13.9 | 8 | 111.2 |
| Copper pulsating heat pipe | 100 | 27.7 | 4 | 110.8 |
| Support (Galvanized) | 50 | 13.9 | 7 | 97.3 |
| Total Embodied energy (kWh) | - | - | - | 439.7 |
Table 5 shows the environmental, enviroeconomic parameters in the waste heat recovery system for a lifespan of 20 years. The results indicated that the CO2 reduction and enviroeconomic parameter of waste heat recovery application were equal to 84.82 tons and 1217.2 $, respectively, during life time. Also, the CO2 emission of the waste heat recovery system during life time based on embodied energy was equal to 879.4 kg.
Table 5
Environmental and enviroeconomic parameter for waste heat recovery system
Parameter | Waste heat recovery system |
Life time (years) | 20 |
Embodied Energy (kWh) | 439.7 |
Annual energy produce by waste heat recovery (kWh/year) | 2120.6 |
CO2 emission during life time (kg) | 879.4 |
CO2 mitigation during life time (ton) | 84.82 |
Environmental parameter (ton \({\text{C}\text{o}}_{2}\)) | 83.94 |
Enviroeconomic parameter ($) | 1217.2 |