Air Conditioning Evaporator Research Articles

Leak Monitoring in Split Duct Air Conditioner Based on Internet of Things

Water accumulation in air conditioning (AC) drain pans can lead to corrosion and subsequent leaks, impacting AC system performance. This study focuses on implementing a monitoring system to track water levels and promptly discharge water to prevent corrosion. Using a research and development approach, the study evaluated the water level sensor's performance in measuring water levels and the pump's effectiveness in discharging water at specific levels, ensuring overall system reliability. The system utilized the NodeMCU ESP8266 microcontroller, a water level sensor, an LCD I2C 16x2 display, and Blynk as a smartphone-based monitoring platform. The findings demonstrated the effective functionality of the device in evacuating accumulated water from the AC evaporator. This was achieved through the activation of a water pump when the water level reached a threshold of 2 cm, thereby preventing potential leakage in the air conditioner's storage gutter.

Investigation of a Combined Refrigeration and Air Conditioning System Based on Two-Phase Ejector Driven by Exhaust Gases of Natural Gas Fueled Homogeneous Charge Compression Ignition Engine

Abstract A natural gas-fueled homogeneous charge compression ignition (HCCI) engine is coupled to an exhaust gas operated turbine driven two-phase ejector cycle to generate power and cooling energy, simultaneously. By establishing a thermodynamic model, the simulation of the proposed system and its parametric analyses are conducted. Energetic and exergetic investigations are carried out to study the role of equivalence ratio, engine speed, condenser temperature, refrigeration evaporator temperature, air-conditioning evaporator temperature, and ejector nozzle efficiency on the thermodynamic performance parameters of the combined cycle. The analysis of two-phase ejector cooling cycle using three working fluids including R717, R290, and R600a is conducted. Results reveal that the thermal efficiency of HCCI engine is increased from 47.44% to 49.94%, and for the R600a operated combined cycle it is increased from 60.05% to 63.26% when the equivalence ratio is promoted from 0.3 to 0.6. Distribution of fuel exergy results show that out of 100% exergy input, in case of R717 operated combined cycle, 139.79 kW (38.72%) is the total exergy output, and 164.21 kW (45.49%) and 57 kW (15.79%) are the values for exergy destruction and exergy losses. It is further shown that change in refrigerant minorly influence the percentages of exergy distribution.

Wettability modification of laser textured copper surfaces applied to phase change heat transfer

Phase change heat transfer allows high heat transfer rates associated with small temperature variations. Given that this technique is employed in several energy and industry applications, such as automotive air-conditioning evaporators, pulsating heat pipes are used for aerospace thermal management and in semiconductor-manufacturing heat exchangers. Although phase change heat transfer has served mankind for more than two millennia, little progress has been made in the last 40 years regarding the basic performance of phase change heat transfer surfaces. However, laser texturing is expected to change this scenario through wettability modification of heat exchanger surfaces, which can lead to heat transfer improvement. In this context, surface texturing of electrolytic copper (a material commonly employed in phase change heat transfer applications) was performed using a nanosecond pulsed fiber laser source associated to a galvanometric scanner. A design of experiments was performed in order to correlate the parameters’ pulse overlapping, laser power, number of scanning repetitions, and pulse duration to their respective machining features. Machining depth and width were evaluated, as well as the surface integrity of the processed region. These analyses were performed by means of white light interferometry, optical microscopy, and scanning electron microscopy. The surface integrity analysis is especially important, since there is a lack of information regarding texturing effects on surface properties, as most studies focus almost exclusively on surface topography and not on the thermal effects that laser texturing can promote to the substrate material. After comprehending the parameter effects on the machining features, surface textures were manufactured and evaluated in order to define their effect over surface wettability, which influences the heat transfer performance. Copper oxide present on the laser generated textures granted them hydrophilicity so that most of the tested textures achieved contact angles of 0°. A cleaning process with H2SO4 was proposed to remove this oxide and decrease the wettability, also allowing hydrophobic surfaces with a contact angle up to 180° to be obtained.

Fabrication and Frosting Properties Study of Surface-Active Agents Coating Based on Nanoporous Aluminum Substrate

In order to solve the frosting and blockage problem of an air conditioning evaporator’s fin in winter, the nanoporous aluminum plates with low surface energy has been proposed in this paper, which are fabricated by an anodizing method and then modified by lauric acid. The nanoporous aluminum plates with different nanoporous diameters ranging from 15 nm to 400 nm are obtained by changing the magnitude of the oxidation current. The surface contact angle of the nanoporous aluminum plates is an important factor influencing its surface frost and condensation. The test results show that the surface contact angle is decreased with the increasing of nanoporous diameter. When the nanoporous aluminum plates are modified by lauric acid, the contact angle is proportional to the nanoporous diameter, and the maximum contact angle can reach about 171°. A set of experimental instruments has been set up to simulate the typical winter climate in northern China, and the frosting properties of the nanoporous aluminum plate’s fin is analyzed by experiment. The results show that increasing the contact angle of aluminum plates can effectively improve its anti-frosting properties. The average frosting rate of the aluminum plate with the contact angle of 60° is about 0.33 [g/(min∙m2)], which is 1.74 times that of the aluminum plate with the contact angle of 171°, whose frosting rate is about 0.19 [g/(min∙m2)]. After taking the expanded aperture processing to the aluminum plate, the diameter with 30 nm, 100 nm, 200 nm, 300 nm, and 400 nm nanoporous aluminum plates are obtained and the polished aluminum plates are also prepared for comparing. Through the test results, the nanoporous aluminum plates are shown to have anti-frosting properties, and the nanoporous aluminum plates with diameter of 300 nm are shown to have the best anti-frosting properties. The calculation mode of frosting growth is derived on the base of experimental results. This research will be helpful in indicating the potential research area of the low-carbon-emission and energy-saving technology for the researchers all over the world.

Simulation and Calculation for the Performance of an Air-conditioning Evaporator with Low Global Warming Potential Working Fluids

A distributed parameter mathematical model is set up for a finned tube evaporator under steady state, the actual flow condition is taken into consideration inside the evaporator in this model. Simulation program of the finned tube evaporator is written with VB language. Comparisons are also conducted between simulation results and data from experiment in the literature, the results show that the model has a good consistency. Based on this model, the characteristics of the flow and heat transfer of low global warming potential(GWP) working fluids R290, HFO1234yf and HFO1234ze in the finned tube evaporator are simulated. When the head-on wind speed, mass flow rate and pipe diameter size are altered, the change situation of heat exchange capacity and pressure drop are analyzed and the performance comparisons between the above low GWP refrigerants and the R410A which are now widely used are carried out. The results show that the R290 has the biggest heat exchange capacity and the HFO1234yf has the smallest under steady wind speed; HFO1234yf and HFO1234ze reach superheat state most easily in the same case. When the pressure drops are same, the mass flow rate of R410A is the maximum and the R290 is the minimum. When the heat exchange capacity is same, the mass flow rate of HFO1234yf is more than others and the R290 is smaller than the others. The model can provide theoretical basis for the optimization design and system matching of low GWP refrigerant finned tube evaporator and the refrigerant alternatives.

Numerical modelling of heat and mass transfer in finned dehumidifier

In several heat exchange devices, phase transition occurs in a small region adjacent to the wall, and the secondary phase is present only in a thin layer running along the wall, allowing for decoupling between the fluid dynamic computation of the core flow and the numerical analysis of the secondary phase. This happens in finned dehumidifier, but also in spray cooling or defogging problems. In a finned dehumidifier, or in air conditioning evaporators, the secondary phase is provided by moist air condensation, and may consist of discrete droplets, continuous film or a collection of rivulets. Several levels of approximation may be adopted, depending on the specific problem: perfect drain assumption requires only the addition of a heat source in the energy equation, otherwise the water layer behaviour has to be taken into account. Furthermore, a heat and mass transfer analogy may or may not be appropriate; in the latter case, the solution of the diffusion equation of humidity is required. Here, different levels of approximation are compared with literature experimental data for condensation over a vertical fin. Results show that thermal resistance and gravity effects, in the considered geometry, are negligible, and the condensate takes the form of a collection of still droplets, rather than a flowing film. This has an effect on the actual heat transfer and water layer build-up, and the variation of temperature along the fin induces some discrepancy with respect to the straightforward application of the heat and mass transfer analogy.

Aerosol Generation by Blower Motors as a Bias in Assessing Aerosol Penetration into Cabin Filtration Systems

In cabin filtration systems, blower motors pressurize a vehicle cabin with clean filtered air and recirculate air through an air-conditioning evaporator coil and a heater core. The exposure reduction offered by these cabins is evaluated by optical particle counters that measure size-dependent aerosol concentration inside and outside the cabin. The ratio of the inside-to-outside concentration is termed penetration. Blower motors use stationary carbon brushes to transmit an electrical current through a rotating armature that abrades the carbon brushes. This creates airborne dust that may affect experimental evaluations of aerosol penetration. To evaluate the magnitude of these dust emissions, blower motors were placed in a test chamber and operated at 12 and 13.5 volts DC. A vacuum cleaner drew 76 m 3 /hour (45 cfm) of air through HEPA filters, the test chamber, and through a 5 cm diameter pipe by a vacuum cleaner. An optical particle counter drew air through an isokinetic sampling probe and measured the size-dependent particle concentrations from 0.3 to 15 μm. The concentration of blower motor aerosol was between 2 × 10 5 and 1.8 × 10 6 particles/m 3 . Aerosol penetration into three stationary vehicles, two pesticide application vehicles and one tractor, were measured at two conditions: low concentration (outside in the winter) and high concentration (inside repair shops and burning incense sticks used as a supplemental aerosol source). For particles smaller than 1 μm, the in-cabin concentrations can be explained by the blower motor emissions. For particles larger than 1 μm, other aerosol sources, such as resuspended dirt, are present. Aerosol generated by the operation of the blower motor and by other sources can bias the exposure reduction measured by optical particle counters.