Substituting Hydrofluorocarbons with natural refrigerants in domestic refrigerators will significantly reduce the direct contributions of fluorinated gases to global warming which will be of great environmental benefit. In this study, the performances of dimethyl-ether (RE170) and its azeotropic mixtures (R510A and R511A) in a refrigeration system were assessed theoretically and compare with that of conventional refrigerant. The study revealed that the three investigated alternative refrigerants exhibited significantly good heat transfer characteristics, low pressure ratio, high latent heat in the liquid phase which resulted in their high thermal conductivity and Volumetric Cooling Capacity (VCC). The thermal conductivity of the refrigerants reduces while the evaporating temperature rises and the value obtained for RE170 was the highest among the four refrigerants studied. The Coefficient of Performance (COP) for RE170, R510A and R511A were higher than that of R134a by 6.20, 10.06 and 3.02 % respectively while their power consumptions per ton of refrigeration were lower than that of R134a by 6.99, 11.04 and 1.47 % respectively. In conclusion, dimethyl-ether and its azeotropic mixtures performed better than R134a in that they have higher thermal conductivity, refrigerating effect, VCC, COP, lower power consumption per ton of refrigeration and hence, they can be considered as suitable replacements for R134a in domestic refrigerator.

The choice of agro waste for the production of briquettes for domestic and industrial cottage utilization depends on the residues’ physical and fuel characteristics. This study investigate the physical and fuel characteristics for both the residues and blends of rice hull, groundnut shell and corncob. The residues were subjected to size reduction process and variance analysis was used to establish the influence of each sample blends.  Different samples of briquettes were produced by blending rice hull (R), groundnut shell (G) and corncob(C) with different ratios of R:G:C respectively using cassava starch as a binder. The residue’ dimensions and densifications of the sample briquettes were determined using standard methods.The results revealed the following ranges of values; For the compressed residues, density (0.075 - 0.099Kg/m3), volume (0.001 - 0.002m3), height (1.0357 - 1.0343m). For the relaxed residues, density (0.049 - 0.210Kg/m3), volume (0.0001 -0.0002m3), height (1.0357 - 1.0343m). The residual density of rice hull, groundnut shell and corncob are 104, 105, and 103 (Kg/m3) respectively. The densification; compressed density (461.22 - 627.24 Kg/m3), relaxed density (285.47 - 393.63 Kg/m3), density ratio (0.56 - 0.66), relaxation ratio (1.52 - 1.79), and compaction ratio (1.46 to 2.01). Blend formulations affected the combustion characteristics of the briquettes, with low moisture briquettes possessing higher calorific values. The briquette formulation containing ratio 50:20:30 of rice hull: groundnut shell: corncob respectively had more positive attributes of biomass fuel such as lower relaxation ratio and high compaction ratio than the control and other formulated briquettes in this study. Generally, significant (p<0.05) differences existed between the samples in almost all the parameters.Keywords: Briquettes, Corn comb, Densification, Fuel Characterization, Groundnut shell, Rice hull.

The diminishing accessibility of wood fuel and the danger of desertification and deforestation call for interest in the use of alternative energy sources. Herein, we studied the properties of bio-briquettes produced from Onyeama coal in Nigeria and groundnut shell used as the desulphurizer, while cassava starch was used as binder with Snail shell. For effective capturing of Sox, snail shell was added. The ratios of coal to groundnut shell (w/w) in the briquette were 90:10, 80:20, 70:30, 60:40 and 50:50, while 1:1, 1.25:1, 1.5:1, 1.75:1 and 2:1 were used as the ratios of calcium to sulphur (Ca/S) in mole/mole. The briquette was then subjected to some physical characteristics and desulphurization was carried out between 300 to 500°C at an interval of 50°C at an airflow rate of 1.2 L/min for 12 minutes. The results illustrated that 88.1% was the highest desulphurization efficiency with 2:1 Ca/S ratio at 500°C. The results showed that the durability ranged between 88.67 and 98.67, the porosity index ranged between 0.19 to 0.41, while the humidity resistance ranged between 95.15 and 99.15%. The best briquette in terms of durability and relative humidity resistance is briquette made of 90% coal with a Ca/S 1:1 desulphurizer ratio, which is preferred for household and cottage industrial applications. However, the use of a Ca/S desulphurizer in the ratio of Ca/S 2:1 at 500 gave better desulphurization.The introduction of SO2 adsorbent also reduced the SOx emitted to the atmosphere.