8.Result & Sisscusion

Chapter 4

Chapter 4

Result and Discussion

Hybrid dryer based on solar and electricity was developed at Department of Renewable Energy Engineering, College of Technology and Engineering, Udaipur. The experimental data during no load and full load testing along with input environmental parameters such as solar radiation, ambient temperature and ambient relative humidity were recorded. The recorded data were analyzed to evaluate the technical and economics performance.

The techno-economical analysis of the system was evaluated in terms of net present worth, benefit cost ratio, payback period and internal rate of return. This chapter deals with the result of the technical and economical feasibility of hybrid drying system for drying of onion flakes. 4.1 Performance Curves for Hybrid Dryer

The no load performance of hybrid dryer was evaluated in two conditions as without electric heater and with electric heater.4.1.1 No load performance A) Without electric heaterThe no load test was carried out to know the trend of various operating parameters with respect to time. The temperature profile at various positions in dryer is presented in fig 4.1. It was observed that the insolation was increased up to 13.00 h and then decreases. Similarly the ambient temperature increased with the day time and slightly decreases in late hours.The temperature of air along the collector length was increased. The temperature at collector outlet and dryer outlet was increased up to 13.00 hours and then decreased. In initial hours of operation there was temperature drop across hot water storage, but later on there was increase in air temperature at hot water outlet. During the no load there was no product in drying unit. This resulted in increase in hot water outlet temperature. The relative humidity of dryer outlet air was less than that of inlet air.

The maximum temperature attained at end of evacuated tube collector was in between 55 to 60C at 14.00 h, when the radiation was also high i.e. 1000 W/m2. From Fig. 4.1 it can be inferred that the temperature rise is the function of solar radiation, ambient temperature and time dependent. Fig 4.1 Performance curve for no load without electric heater

B) With electric heater

The variation of operating parameters during no load with electric heater was represented in Fig. 4.2. The trend of various parameters over time during no load with electric heater was same as that of without heater. The temperature of hot air was set at 60C. The electricity consumption was approximately 8 units in 10 h. 4.1.2 Full load performance

The full load testing is presented in Fig. 4.3. The temperature of drying chamber was set at 60C. Electric heater was provided to supply heat when temperature falls below 60C.It was observed that during the full load the maximum temperature at ambient was 40.2C. The maximum solar radiation was 1020 W/m2 at 13.00 hrs. The maximum hot water inlet temperature was 62 C. The temperature of drying chamber inlet and all of the three trays varies between 60 to 65 C during the day.

Fig4.2 Performance curve for no load with electric heater4.1.3 Variation in moisture content

Average moisture content (w.b.) during full load test is presented in Fig. 4.4. Within 10 hours, the onion flakes were dried from moisture content of 87 % to 10 % (w.b). At initially, moisture evaporates rapidly and then it is removed slowly.

4.1.4 Variation in drying rate with respect to time

The drying rate for the onion flakes was estimated from the difference in its moisture content in a given time interval and expressed as gram water evaporated per hour. It has been observed that drying rate of onion flakes was decreased as moisture content is decreases. Drying rate of onion flakes varies between 0.65 to 2.14 as shown in fig. 4.5.

Fig 4.3 Performance curve for full load testing

Fig 4.4 Variation in moisture content with respect to time

Fig 4.5 Variation in drying rate with respect to time4.1.5 Variation in electricity consumption

Electricity consumption during full load testing was 8 kWh. Electricity consumption is higher in starting as compared to during 13:00 h. at initial hours water temperature in heat exchanger cum storage unit is low, due to this heat requirements are met through electric heater. It is clearly shown in the graph that as sunshine increases, energy supply through electric heater decreases.

Fig 4.6 Variation in hourly electricity consumption with respect to time

Plate 4.1 Onion flakes before drying

Plate 4.2 Onion flakes after drying4.2 Techno Economics of Hybrid Dryer

The techno economics were carried out on the basis of assumptions made in section 3.10. The various economic indicators are presented in Table 4.1.Table 4.1 Economic indicator for Hybrid dryer

Sr. No.Economic indicatorValue

1Net present worthRs. 3,48,270.71

2B/C ratio1.6

3Payback period1 year 8 months

4IRR %71.83

The cost benefit ratio was found to be 1.6 with a payback period of 1 year 8 months. It can be inferred that the developed dryer is technically as well as economically feasible. The higher percentage of the internal rate i.e.71.83 per cent of return indicated the good economical return of the investment.

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