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• A thermoelectric refrigeration system with ionic wind fans operates ultra-quietly. • Optimal operational parameters were obtained to maximize the performance. • Experimental COP was equivalent to the system with mechanical fans. • Experimental refrigeration capacity reached 8 W under 30 K difference. Conventional compression refrigeration systems generate considerable noise and vibration. The noise results in serious, negative impacts on people. Thermoelectric refrigeration technologies are considered a potential way to overcome these challenges. A novel thermoelectric refrigeration system, wherein thermoelectric chips are coupled with ionic wind fans, is proposed. Its performance was experimentally investigated and compared with theoretical results. The actual operating noise of the thermoelectric refrigeration system is only 4.2 dB(A), which is much lower than the maximum noise value that does not affect sleep. From experiments under different operating conditions, the optimal operating voltage of the thermoelectric chip is 5.5 V at 283.15 and 313.15 K on the cold and hot sides. The maximum coefficient of performance (COP) values reaches 0.28 and 0.31, which are equivalent to those of a system coupled with mechanical fans. Additionally, an ionic wind fan has an optimal operating voltage of 10.8 kV to maximize its air supply efficiency. Notably, such an operating voltage might be distinguished from the optimal voltage that achieves maximum operational performance for the new system. When the operating voltage of the thermoelectric chip is 5 V, the optimal operating voltage to obtain a maximum COP of 0.31 is 11.1 kV. Moreover, the experimental refrigeration capacity is greater than 8 W. The new system shows the ultra-quiet ability to operate at a large refrigeration capacity, and has good potential in applications, such as advanced refrigeration, building air-conditioning and ventilation systems. [ABSTRACT FROM AUTHOR]

The frequent infiltration through doorways accounts for a very large proportion of the total heat load of cold stores. Understanding the influence factors, along with wider range of experiments, clearly supports the accurate prediction and cuts down the infiltration. This paper provides a series of experimental investigations on the infiltration under different conditions. The experiments take factors of various door opening sizes, temperature differences and on/off of the cooling fans into account. It is observed that the infiltration flow rate stays steady while the indoor temperatures of the local probes change vigorously. The infiltration air volume changes linearly with the door open time, whether the cooling fans are turned on or off. Moreover, the air mixture effect related to the cooling fans can counteract the infiltration process. [ABSTRACT FROM AUTHOR]

Abstract: Freezing process efficiency is affected by the required conditions to keep the air flow and temperature at the product surface. The objective of this work was to obtain results on comparative studies with air exhaustion and blowing using an experimental portable forced-air freezing tunnel. The device was designed to improve cooling rates inside storage room without the need for a cooling/freezing tunnel. A heterogeneity factor was proposed for air circulation evaluation and compared with convective heat transfer coefficient (h ef) values. Lower modules of heterogeneity factor values represent smaller temperature differences among samples. Comparing two different air flow processes, heterogeneity factor values were similar for regions where the cooling air could flow without obstructions. However, larger differences were observed for regions with hampered air circulation. Results indicated that the air distribution, as well as the heat transfer, occurs more uniformly around the products in the exhausting process than in the blowing system. [Copyright &y& Elsevier]

Abstract: Low-noise centrifugal fans are developed by modifying the linear trailing edge lines of the fan blades into inclined S-shaped lines. The noise reductions achieved by using the inclined S-shaped trailing edges in the existing fans are confirmed by comparing the predicted BPF noise components of the developed fans with those of the existing fan. In addition, the turbulent kinetic energy of the fluid for the inclined S-shaped fans is predicted to be less than that for the existing fan. Finally, experiments using four prototype fans show that the levels of broadband noise from the newly developed fans are less than those of noise from existing fans. An additional experiment performed by using a selected low-noise fan installed in a household refrigerator show that the overall noise from the new fan is reduced by approximately 2.2dB in comparison with that from the existing fan in the refrigerator. [Copyright &y& Elsevier]

Abstract: The internal blade-passing frequency (BPF) noise of a centrifugal fan in a household refrigerator is computed using a hybrid method. The unsteady flow field of the centrifugal fan in a duct is predicted by solving the incompressible Reynolds-averaged Navier–Stokes equations with conventional computational fluid dynamics techniques. The principal sources of noise are then extracted from the predicted flow field through the acoustic analogy. Finally, the internal BPF noise is predicted using the modeled sources in combination with the boundary element method. A parametric study using this hybrid technique shows that the BPF noise levels predicted for various non-dimensional cutoff distances closely follow the experimental data. Based on this result, a low-noise design for the centrifugal fan is proposed. A BPF noise reduction of approximately 3 dB is achieved in comparison with the original model, which is in good agreement with the prediction using the hybrid techniques. [Copyright &y& Elsevier]

Abstract: A commercial fan coil has been experimentally studied in this work in order to assess its behaviour when ice slurry is used as secondary refrigerant. Experimentally obtained results have been compared to theoretical prediction obtained using the correlations proposed in previous papers in order to verify them. Several reasons have been reported to explain the deviation of fan coil behaviour from that expected and which make the direct application of ice slurry inappropriate in the fan coil studied. In order to avoid those problems and to establish a comparison between two secondary refrigerants with similar cold storage capacity, ice slurry direct application has been compared to ice slurry indirect application – only carrier fluid, without ice particles, flowing through the fan coil. The most remarkable conclusion obtained is that indirect application improves the behaviour of the fan coil studied for all the cases analysed, overcoming the problems reported for direct application. [Copyright &y& Elsevier]