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The densities and viscosities of ethyl heptanoate and ethyl octanoate were measured at temperatures ranging from 303 to 353 K and at pressures ranging from 0.1 to 15 MPa. The expanded uncertainties of density and the relative expanded uncertainty of viscosity are better than 5 kg·m–3 and 0.015, respectively. Experimental results show that the densities and viscosities of the two fatty acid ethyl esters increase with the increasing pressure and decrease with the increasing temperature. The density data were correlated using the Tait equation, and the viscosity data were correlated using the Andrade–Tait model. The average absolute relative deviations between the experimental data and the calculated results for the densities and viscosities were less than 0.03% and 0.47%, respectively.

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Blending methyl ester biodiesel and ethyl ester biodiesel can improve the properties of biodiesel. The densities and viscosities of the mixtures of methyl dodecanoate plus ethyl octanoate with various compositions were reported at temperatures from 303.15 to 323.15 K and at pressures up to 15 MPa. Experimental data show that the densities and viscosities of the mixtures of methyl dodecanoate plus ethyl octanoate will increase when temperature decreases or pressure increases. Ethyl octanoate can effectively reduce the viscosity of methyl dodecanoate with a small change in density. Correlations for the data of density and viscosity were proposed with maximum absolute relative deviations less than 0.04 and 5.8%, respectively.

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In order to evaluate the effects of variable semiconductor cross section on the cold-end temperature of thermoelectric cooler (TEC), the numerical model of the cold-end temperature field of TEC with variable semiconductor cross section was established using the lattice Boltzmann method (LBM) in this work, Firstly, the Chapman-Enskog expansion method was used to derive the LBM model and build the parameter connection between the continuous equation and the discrete model. Secondly, nine different types of cross section of TECs were designed to calculate cold-end temperature field at different electric current. Finally, it is found that increasing the cross-sectional area of the cold end will decrease the minimum cold-end temperature, but increase the optimal current. While maintaining the same cross-sectional area of the cold end, decreasing the hot-end cross-sectional area has less effect on the minimum cold-end temperature but decreases the optimal current. In order to increase the cooling capacity, the cross-sectional area of the cold end can be appropriately larger. TEC of type 2# with a larger cross section at the cold end reduces the cooling temperature by 15.38 K at the cost of a coefficient of performance reduction of 0.021.