Background
Solar dryers are devices used to eliminate the moisture content from crops, vegetables, and fruits.
A solar dryer consists of a box made up of easily available and cheap material like cement, galvanized iron, brick, and plywood.
The top surface of the dryer is covered by transparent single and double-layered sheets.
Thermodynamic analysis of a mixed-mode solar dryer
During is the process of extracting heat from a substance using a source of heat. In this paper, a discussion is made of how a solar dryer operating in a mixed-mode configuration can be used to dry out substances. A mixed-mode solar dryer combines several modes of heat extraction to achieve drying. These include radiation, convection, and conduction.
A mixed-mode solar dryer is shown in figure 1:
Figure 1:mixed-mode solar dryer
The main components of the dryer are the air heater and a drying chamber. We initially set the initial thermodynamic properties of the fluid (air) to be . These represent the temperature, relative humidity and specific humidity respectively. After absorbing heat energy, these values change to be .
It is worthy noting that this chamber operates by heating up air and then allowing the air to blow over the substances that need to be dried. The drying process is illustrated in figure 2 below:
Figure 2:solar drying process
The mass balance equations for the dryer can be written as:
For the product,
————————-(1)
For the air,
————————–(2)
For the water,
——–(3)
Performing energy balance for the system we get;
—–(4)
Where,
Where,
—————–(5)
———————————–(6)
The heat loss through the dryer is given as:
——–(7)
The overall efficiency of the dryer is given by:
——————(8)
On the other hand, the energy efficiency is given by:
—(9)
From the analysis, we see that the energy and the overall efficiencies inn the air heater are lower than those in the drying chamber.
Solveig a problem with some numerical assumptions.
2
The post Background Solar dryers are devices used to eliminate the moisture content from appeared first on PapersSpot.
