Control of frost formation in refrigeration applications utilizing the electrohydrodynamic technique-fundamentals, past work and prospects

Abstract

Frost is an undesirable problem in energy conversion and engineering applications because it negatively affects the operating system performance by reducing the heat transfer for energy conversion systems and the coefficient of performance (COP) for refrigeration and air conditioning (HVAC) equipment. Among the various frost prevention or removal techniques, electrohydrodynamics (EHD) is an active frost prevention and removal technique that has been studied since the 1970s. This review paper clarifies the fundamentals of EHD, while offering a comprehensive review of the works published in the literature regarding both the influence of EHD on frost growth control and its effectiveness on frost removal. It is observed that while individual research works have drawn conclusions on the specifics of EHD for frost control and removal, there is no consensus in the literature on the specific effects of some of the critical parameters associated with EHD phenomena, such as the influence of electric field intensity and the use of AC and DC voltage, which can both affect frost growth. In addition, no baseline for comparison has been established, making it difficult to compare the results of various investigators. Finally, prospects and conclusions are discussed.This article is part of the theme issue 'Heat and mass transfer in frost and ice'.

Keywords: HVAC; electrohydrodynamics (EHD); frost; frost control; frost prevention; ice; refrigeration.

Figure 1.

Plasma classification.

Figure 2.

Basic DBD configurations.

Figure 3.

Schematic of CD.

Figure 4.

(A) The behaviour of charged and neutral particles in a uniform electric field; (B) the behaviour of charged and neutral particles in non-uniform electric fields.

Figure 5.

Ice-crystal dendrites grown from supersaturated air at −15°C without the electric field presence (a), and with the presence of electric field (b). From Libbrecht & Tanusheva [29], used with permission from the American Physical Society.

Figure 6.

An ‘electric’ needle growing at −4°C under the influence of an electric field. From Bartlett et al. [30] used with permission from Springer Nature.

Figure 7.

The ice-crystal growth rate as a function of an applied electric field. Data from Crowther [35], used with permission from the Elsevier.

Figure 8.

(a) Schematic diagram of frost crystal morphology under different electric fields, (b) the jumping speeds of frost crystals at different electric field strengths, (c) and frost mass on the frozen droplet at different electric fields. Data and figures from Xu et al. [38], used with permission from Elsevier.

Figure 9.

The influence of electric field intensity on frosting weighs for (a) a copper plate under AC and DC electric fields and (b) for a PTFE surface under DC electric fields. Data from [46].

Figure 10.

(a) Schematic of electrode gap (b) and influence of the applied AC voltage frequency on frost mass reduction (R) Ta = 0°C, Tp = −30°C, L = 5.0 mm, V = 14.5 kV. Data from Tudor et al. [39], used with permission from Taylor and Francis.

Figure 11.

(a) Schematic of the test section and (b) the maximum frost thickness as a function of time under the influence of electric polarity. Data from [41]. From Wang et al. [41], used with permission from Elsevier.

Figure 12.

Freezer test chamber (a) and test evaporator with wire electrodes (b). Reproduced with permission from the authors [52].

Figure 13.

Results for the influence of cold plate temperature (a) and the ambient temperature (b) on frost-layer thickness. Data from [42].

Figure 14.

Layout of electrodes (left) and mass reduction index as a function of the electric field intensity for all the tested electrodes (t_A = 10°C, RH = 75%, t_S = −3°C, v = 3 m/s and t = 7200 s) (right). Data from Joppolo & Molinaroli [53] used with permission from ASHRAE.