Difference between revisions of "Team:Jilin China/Model/For Practices"

Background

For the potential use to lower down fermentation temperature, our RNA thermosensors can realize the energy conservation in fermentation production theoretically. Hence, we modeled the energy saving process based on the data from Ground.

The schematic of fermenter has been shown below (Figure 1). Mixing system helps raw material to contact sufficiently with oxygen. And the heating jacket with flow inside is stable heat source of fermenter. The heat transfer with air should be considered as the main energy consumption. As a result, estimating the heat dissipated power is the first step to get the amount of energy saving.

Figure 1. Fermenter

Methodology

1. The Features

Here are the features of the fermenters in Ground from HP(Table.1)

material	304 stainless steel
Radiating area	20.4 m2
Capacity	6t
Thermal conductivity	16W·m-1·K-1
Board thickness	50 mm

Here are the features of parameters in yogurt fermentation(Table.2)

Real fermentation temperature	42℃
Ideal fermentation temperature	39℃
Fermentation duration	4h
Environment temperature	25℃

2. The simplifed radiating system

Heat equation represents temperature history in a certain area:

$$\left\{ \begin{array}{}{\partial{u}\over{\partial{t}}}={k\over{c\rho}}{{\partial^2u}\over{\partial^2}{x^2}}\\ u(0,t)=a \\ u(x,0)=b\\ u(\delta,t)=c \end{array} \right. $$

u=u(t,x) represents temperature, which is a function of time variable and space variable. ∂u/∂t is the rate of change of temperature with time. x is the space variable. a, b is boundary condition, while c is the initial condition.

As an instance, we used classical difference method to get the temperature distribution of 304 stainless steel board at different heat transfer time(Figure 2).

Figure 2. Temperature distribution of 304 stainless steel board at different heat transfer time. Boundary condition: a=42℃, b=25℃. Initial condition: c=25℃.

According to this, the curve is close to a straught line. To simply the system, we assumpted the heat transfer process is relatively stable, which follows Newton’s law of cooling(Figure. 3).

Figure 3. the Radiating System

3. Thermodynamic

Heat flux: A flow of energy per unit of area per unit of time. $$Φ_{q}=-k{{dT(x)}\over{dx}}$$ k means thermal conductivity, which is the property of a material to conduct heat. T(x) is a function of correlated with temperature distribution. Here, x represents the distance between one certain point and interior surface.(Figure 3)

Figure 4. x represents the distance between one certain point and interior surface.

Heat dissipated power: $$P=Φ_{q}A$$ A is the radiating area.

Results

Figure 5. A) and B) show the temperature distribution on the fermenter board under different fermentation temperature(T^f). C) shows the heat flux(Φ) changing under different fermentation temperature.

According to graph C), we calculated the energy saving while the fermentation temperature lowering down.

Figure 6. shows the change of power to overcome heat dissipation during fermentation with temperature rise. ΔE represents the energy saving by one degree decline of fermentation.

Conclusions

From the figures above, we got the amount of energy saving per degree down. According to Enterprise energy saving calculation method (GB/T13234-91), the energy measurement transferred into standard coal(see Table. 3).

Real energy cost	21kg coal/t
1℃ saving	0.20kg coal/t
Energy saving ratio	0.95%