Air-cooled chiller screening noise analysis with preliminary building project information

For Inter-noise 2018, the author submitted a paper proposing techniques to derive reasonable preliminary estimates of building project stationary noise emission levels from sparse but available data that may seem unrelated to noise or vibration such as gross square footage (GSF), expected occupancy, and land use or function. Results from these predictions would be used to support or refine established buffer distances between exposed outdoor heating, ventilating, and air-conditioning (HVAC) system noise sources and nearby noise-sensitive receptors, helping planners tasked with ambitious infill or growth goals better fit building projects into complicated campus development puzzles. This paper provides supplemental guidance by linking the same preliminary building project GSF, occupancy, and function information to estimates of cooling load (expressed as refrigeration tonnage) and thus an additional HVAC consideration not discussed in the author's previous study. When such refrigeration relies upon air-cooled condensers installed outdoors on building rooftops or at grade, substantial noise sources are introduced to the environment. Thus, this new study shares data and methodology to help expand the value and utility of the previous work and potentially provide more comprehensive building HVAC noise estimates for use by building developers and planners.

Experimental performance comparison between circular and elliptical tubes in evaporative condensers

In refrigeration systems, evaporative condensers have two main advantages compared to other condensation heat exchangers: They operate at lower condensation temperature than traditional air-cooled condensers and require a lower quantity of water and pumping power compared to evaporative towers. The heat and mass transfer that occur on tube batteries are difficult to study. The aim of this work is to apply an experimental approach to investigate the performance of an evaporative condenser on a reduced scale by means of a test bench, consisting of a transparent duct with a rectangular test section in which electric heaters, inside elliptical pipes (major axis 32 mm, minor axis 23 mm), simulate the presence of the refrigerant during condensation. By keeping the water conditions fixed and constant, the operating conditions of the air and the inclination of the heat transfer geometry were varied, and this allowed to carry out a sensitivity analysis, depending on some of the main parameters that influence the thermo-fluid dynamic phenomena, as well as a performance comparison. The results showed that the heat transfer increases with the tube surface exposed directly to the air as a result of the increase in their inclination, that has been varied in the range 0–20°. For the investigated conditions, the average increase, resulting by the inclination, is 28%.

Reduction of dust deposition in air-cooled condensers in thermal power plants by Ni–P-based coatings

One of the largest problems with most current thermal power plants is the cooling efficiency. This paper aims to massively reduce fuel consumption and heat wasted in thermal power plants and hence CO2 emissions by resolving fouling issues associated with air-cooled condensers. In order to reduce the dust fouling deposition in the air-cooled condensers, the finned flat tubes were coated with nickel−phosphorus and nickel−phosphorus−polytetrafluoroethylene (Ni–P-PTFE) by an electroless coating technology. The anti-fouling performance of the coated tubes was investigated using the field operation parameters of air-cooled condensers, and the influence of the surface energies of the coatings on the dust adhesion was also investigated. The results demonstrated that the Ni–P coated finned tubes performed best, which reduced fouling resistance by 83.3% compared with the untreated finned tubes. The Ni–P coatings have potential applications in thermal power plants for reducing heat exchanger fouling and hence significantly decreasing waste heat and CO2 emissions. Graphic abstract

Modeling a Large Air-Cooled Condenser

This study reports on a modeling strategy for large Air-Cooled Condensers (ACCs). A large 64-fan ACC was modeled under various crosswind conditions that investigated the ACC’s specific axial flow fan configuration. The ACC model was developed in two parts, an axial flow fan model and a heat exchanger model. The axial flow fans were modeled using an Actuator Disk Model (ADM). The heat exchangers’ pressure drop was modeled using the Darcy-Forchheimer porosity model, and the Effectiveness Number of Transfer Units (ε-NTU) method was used to determine the air heat transfer rate. The ACC was configured using two different axial flow fans, identified in this study as the L-fan and the N-fan. Comparatively the L-fan has a steeper fan static pressure characteristic curve than that of the N-fan, at the cost of a greater shaft power consumption. Under normal operating conditions the average heat-to-power ratios were calculated at 89.91 W/W for the L-fan and 102.48 W/W for the N-fan. Under crosswind conditions of 9 m/s the heat-to-power ratios of the leading edge fan-units decreased by 80.6% and 87.0% for the L-fan and N-fan respectively. However, at the fan-units immediately downstream of the leading edge the heat-to-power ratios only decreased by 34.1% for the L-fan and 64.2% for the N-fan.

Experimental Testing on an Air-Cooled Condenser Motor, Gearbox and Fan

The majority of South Africa’s electricity is generated from coal-fired power stations. After expansion through the turbine stage the heated steam is condensed by air-cooled condensors (ACCs). In water scarce areas air-cooled condensers are used to reject heat by means of convection through an array of fans that force air over the heated steam tubes positioned in a A-frame structure above the fan. The ACC system consists of an induction motor, two-stage gear reducer and an axial fan. For this research, the rotational velocity of the gearbox’s output shaft is measured as well as the bending and torsional strain experienced during different stages of operation. A proximity sensor and various sets of strain gauges are used to record the measurements respectively. Testing was conducted at three different sites that utilize different control methods for the induction motors. The purpose of testing at different sites was to evaluate the effectiveness of each start-up control system and its application inside an ACC. The results obtained in each of the three cases are quite clear that any motor controller is beneficial to the overall system simply due to the reduced inrush current and torque peaks.