Sink Outlet Research Articles

A ‘Tuba Drain’ incorporated in sink drains reduces counts of antibiotic-resistant bacterial species at the plughole; A blinded, randomised trial in 36 sinks in a hospital Outpatients with a low prevalence of sink colonisation by antibiotic-resistant species

Multi-resistant Gram-negative bacteria (GNB) survive in hospital drains in traps that contain water and may ascend into the sink because of splashes, or biofilm growth. To investigate whether the 'Tuba Drain' (TD) a long, bent, continually descending copper tube between the sink outlet and the trap prevents the ascent of bacteria. After initial laboratory tests confirmed that the TD prevented bacteria in the U-bend from splashing upwards into the sink outlet, TDs were assessed in a randomised, blinded trial in a hospital out-patients built in 2019. Sinks were paired into those with a similar clinical exposure and each member of each pair was randomised to receive either new, standard plumbing up to and including the trap (18 sinks) or the same new standard plumbing but including the TD inserted between the sink outlet and trap. Bacterial counts in swabs from the sink outlets were determined blindly before and monthly after the plumbing change for a year. GNBs that are associated with clinical infection and carriage of resistance genes, Pseudomonas aeruginosa, Acinetobacter baumanii, Stenotrophomonas maltophilia and all Enterobacteriales spp were the organisms of primary interest and termed target bacteria. The TDs fitted into the required spaces and functioned without problems. The geometric means (over months) of the counts of target bacteria in TD-plumbed sinks was lower than those in their paired controls p= 0.012 (sign test 2 tailed). Prevalence of target bacteria in sinks was low. TDs were effective for reducing target bacteria in sinks.

Experimental study on startup characteristics of instant heat pump water heater with non-azeotropic natural blend

The effects of starting mode and outlet temperature of heat sink (OTHS) on the starting performances of direct-heated heat pump water heater using natural blend were investigated experimentally. The results indicated that both starting mode and OTHS had notable impact on starting time of transient performance parameters. Both warm start and lower OTHS helps to quickly obtain hot water at the target temperature, mainly because the system startup time in the warm start was 16.73 % shorter than that in the cold start and the system gained the shortest startup time (1015 s) in low temperature condition. The transient heat sink outlet temperature had a rapid temperature rise section and a slow temperature rise section (STRS), and the STRS consumed 56.58 %–66.67 % of the system starting time, so the improvement of STRS is the key to realize the fast startup. The effects of startup mode on the trends of transient performance parameters were memorably different, but the OTHS had no apparent effect on their trends. The transient refrigerant pressures and transient refrigerant temperatures had the fluctuations. The transient suction pressures had the minimum values (0.3925–0.5575 MPa), and both cold start mode and higher OTHS resulted in a decrease in the minimum value.

Experimental Performance Comparison of High-Glide Hydrocarbon and Synthetic Refrigerant Mixtures in a High-Temperature Heat Pump

Several theoretical studies have predicted that refrigerant mixtures with glides of more than 20 K can yield COP improvements in heat pumps for operating conditions where the temperature difference between the heat source and heat sink is large, but experimental validations and quantifications are scarce. The application of high-glide mixtures (>20 K) in industrial heat pumps in the field is, therefore, still hampered by concerns about the behavior and handling of the mixtures. This study experimentally investigates hydrocarbon (HC) mixtures R-290/600 (propane/butane) and R-290/601 (propane/pentane) and compares them to previously tested mixtures of synthetic refrigerants. Comprehensive evaluations are presented regarding COP, compressor performance, pressure drop, heat transfer, and the possibility of inline composition determination. The mixtures were tested over a range of compositions at a source inlet temperature of 60 °C and a sink outlet temperature of 100 °C, with the heat sink and heat source temperature differences controlled to 35 K. R-290/601 at a mass composition of 70%/30% was found as the best mixture with a COP improvement of 19% over R-600 as the best pure fluid. The overall isentropic compressor efficiency was similar for HC and synthetic refrigerants, given equal suction and discharge pressures. Pressure drops in heat exchangers and connecting lines were equal for synthetic and HC mixtures at equal mass flow rates. This allows higher heating capacities of HC mixtures at a given pressure drop (mass flow rate) due to their wider vapor dome. A previously developed evaporator heat transfer correlation for synthetic refrigerant mixtures was applicable to the HC mixtures. A condenser heat transfer correlation previously fitted for synthetic refrigerants performed significantly worse for HC mixtures. Composition determination during operation and without sampling was possible with a deviation of at most 0.05 mass fraction using simple temperature and pressure measurements and REFPROP for thermodynamic property calculations. Overall, high-glide HC mixtures, just like mixtures of synthetic refrigerants, showed significant COP improvements for specific operating conditions despite a decreased heat transfer coefficient. Potential problems like composition shift or poor compressor performance were not encountered. As a next step, testing high-glide mixtures in pilot-plant installations is recommended.

Experimental investigation on system performance of an instant heat pump water heater with combined condenser

To solve the problem of poor heat transfer effect in the subcooled region of integrated condenser, a combined condenser for instant heat pump water heater (IHPWH) was proposed and designed based on the condenser design model, aiming at obtaining an optimal design method of condenser. The off-design performances of heat pump water heater (HPWH) with a combined condenser (HPWHCC) and HPWH with an integrated condenser (HPWHIC) were investigated and compared based on the Mopt IHPWH test unit, aiming at verifying the feasibility of using a combined condenser replacement of an integrated condenser in the IHPWH. The results show that the heat transfer area of combined condenser is only 83.33 % of that of integrated condenser. Compared with the HPWHIC, the HPWHCC achieves basically equivalent COP and heating capacities and slightly higher discharge temperatures under variable heat sink outlet temperature (HSOT) condition and variable heat sink inlet temperature (HSIT) condition. Therefore, the combined condenser has the obvious potential to replace the integrated condenser in the IHPWH. The HSOT has a remarkable influence on the COP of HPWHIC and HPWHCC but a small influence on their heat capacities, while the HSIT has a small influence on their COP and heat capacities.

Experimental Study on the Feasibility of Quick Startup of Instant Heat Pump Water Heaters Based on Active Control of Heat Sink Flow Step

The influence of flow step ratio (FSR) on the startup characteristics of instant heat pump water heaters (IHPWHs) with natural mixture M (R744/R290 (12/88)) under nominal conditions was studied experimentally to verify the feasibility of a new quick startup method. The results show that the FSR had a marked effect on the startup time of system performance parameters. Under the optimal FSR of 0.6, the shortest system startup time and available hot water supply time were 700 s and 250 s, respectively, which were markedly shorter than those in the conventional startup. Therefore, rapid startup of the system and rapid production of usable domestic hot water can be realized by controlling the flow step. The influence of flow step on the variation trend of system performance parameters was obviously different, and there was no slow warming section for the heat sink outlet temperature (HSOT) under three FSRs. The HSOT, heating capacity, and high pressure side pressures had the maximum values in the quick startup, and the maximum values were obviously affected by the FSR. The FSR had no marked effect on the minimum suction pressure. The refrigerant pressures and refrigerant temperatures fluctuated markedly in both rapid and conventional starts.

Backpropagation Neural Network‐Based Prediction Model for Fuel Cell Thermal Management System

The temperature prediction of fuel cell thermal management systems (FCTMS) has been the focus of research in fuel cell vehicle. Herein, a prediction model of FCTMS based on the backpropagation neural network is proposed. Predictive models are applied to fuel cell TMSs for predicting temperature changes within the system. First, the fuel cell TMS is established based on Amesim software and verified by using experimental data. Then a prediction model is established based on the simulation data of the system model. After the validation calculation, the highest accuracy of the stack temperature prediction was found, with a relative error of 0.75%. The heat sink outlet temperature prediction accuracy is the worst, with a relative error of 4.3%. The mean square error of the overall output of the prediction model is 0.043, and the mean absolute percentage error of the three results is 0.23%, 0.48%, and 0.16%. Both are below 5%. Therefore, the prediction model has more precise prediction performance, which helps the parameter study and control decision setting of FCTMS.

Influence of operating parameters on the COP of an R600 high-temperature heat pump

Process heat supply by high-temperature heat pumps exploiting waste heat is an effective method for enabling the decarbonisation of industrial processes. Key aspects for the application of this technology are the supply temperature levels and efficiencies that can be achieved. This work investigates an R600 (n-butane) high-temperature vapour compression heat pump (HTHP) capable of utilizing waste heat at temperature levels between 40 and 60°C and lifting it to supply temperatures between 110°C in sub-critical and 160°C in trans-critical operation. The HTHP prototype is designed as a single-stage cycle, comprising an inverter-driven suction-gas-cooled reciprocating compressor, low-pressure accumulator and internal heat exchanger (IHX) for suction gas superheating. The influence of the operating parameters high pressure and suction gas superheat (“internal parameters”) plus the heat source temperature, the heat sink inlet and outlet temperatures and the compressor speed (“external parameters”) on the COP and heating capacity are studied using data from both the prototype and the simulation model. The optimum high pressure depends on the operating conditions, an increase of suction gas superheat increases the COP. In sub-critical operation, a heating capacity of 30.7 kW at a COP of 4.4 is reached at a source inlet temperature of 60°C heating the sink from 80 to 110°C. Trans-critical operation enables a heat sink outlet temperature of 160°C, offering a heating capacity of 24.2 kW at a COP of 3.1.

Identification of Existing Challenges and Future Trends for the Utilization of Ammonia-Water Absorption–Compression Heat Pumps at High Temperature Operation

Decarbonization of the industrial sector is one of the most important keys to reducing global warming. Energy demands and associated emissions in the industrial sector are continuously increasing. The utilization of high temperature heat pumps (HTHPs) operating with natural fluids presents an environmentally friendly solution with great potential to increase energy efficiency and reduce emissions in industrial processes. Ammonia-water absorption–compression heat pumps (ACHPs) combine the technologies of an absorption and vapor compression heat pump using a zeotropic mixture of ammonia and water as working fluid. The given characteristics, such as the ability to achieve high sink temperatures with comparably large temperature lifts and high coefficient of performance (COP) make the ACHP interesting for utilization in various industrial high temperature applications. This work reviews the state of technology and identifies existing challenges based on conducted experimental investigations. In this context, 23 references with capacities ranging from 1.4 kW to 4500 kW are evaluated, achieving sink outlet temperatures from 45 °C to 115 °C and COPs from 1.4 to 11.3. Existing challenges are identified for the compressor concerning discharge temperature and lubrication, for the absorber and desorber design for operation and liquid–vapor mixing and distribution and the choice of solution pump. Recent developments and promising solutions are then highlighted and presented in a comprehensive overview. Finally, future trends for further studies are discussed. The purpose of this study is to serve as a starting point for further research by connecting theoretical approaches, possible solutions and experimental results as a resource for further developments of ammonia-water ACHP systems at high temperature operation.

Experimental investigation on a heat pump water heater using R744/R290 mixture for domestic hot water

The natural eco-friendly mixture of R744/R290 was investigated to replace R22 in a fully instrumented water-water heat pump test rig. The test results show that the R744/R290 mixture with optimum concentration of 12%/88% (Mopt) is the suitable working medium for heat pump water heaters because of its higher COP and heating capacity than those of R22 under variable conditions as well as the nominal working condition. The heat pump system with Mopt can supply higher temperature hot water and promote compressor lifetime in substitution of R22. The test results also reveal that the heating COPs of heat pump system with Mopt are 4.98–11.00% higher than those of R22 at the heat sink outlet temperature ranging from 45 °C to 65 °C, and the heat sink outlet temperature has obvious effect on the system efficiency but little on the heating capacity.

Performance assessment of heat pump water heaters with R1233zd(E)/HCs binary mixtures

The eco-friendly zeotropic mixtures of R1233zd(E) with four hydrocarbons were investigated to replace the traditional refrigerants (R22 and R134a) in heat pump water heaters. Under the nominal working condition, the performances of heat pump were analyzed by establishing the mathematical model based on the fixed pinch point temperature difference in the heat exchangers. The results show that both blends R1233zd(E)/R1270 and R1233zd(E)/R290 are suitable drop-in candidates of R22 or R134a for heat pump water heaters. The R1233zd(E)/R1270 with optimal mass fraction 16%/84% demonstrates the best system COP which is respectively 2.13% and 10.14% higher than those of R22 and R134a. The temperature glide feature of zeotropic mixture influences on the system COP greatly in matching both heat transfer processes in condenser and evaporator. The heat sink outlet temperature influences the system COP greatly that when it is 45, 55 or 65°C, the corresponding maximum system COP is 5.803, 4.646 or 3.888 with R1233zd(E)/R1270 and 5.724, 4.535 or 3.757 with R1233zd(E)/R290 respectively. Also, the optimal fraction of R1233zd(E) shifts to a slightly higher value with the rise of heat sink outlet temperature.

Analyses of the Effect of Cycle Inlet Temperature on the Precooler and Plant Efficiency of the Simple and Intercooled Helium Gas Turbine Cycles for Generation IV Nuclear Power Plants

Nuclear Power Plant (NPP) precooler coolant temperature is critical to performance because it impacts the work required to increase the coolant pressure. Variation of the coolant temperature results in varied precooler hot gas temperatures, which are cooled before re-entry. For recirculation, the heat sink (usually sea water), could exit the precooler at unfavourable temperatures and impact the re-entering coolant, if not recirculated properly at the source. The study objective is to analyse the effects of coolant inlet temperature on the heat sink and cycle efficiency. The cycles are Simple Cycle Recuperated (SCR), Intercooler Cycle Recuperated (ICR), and Intercooled Cycle without Recuperation (IC). Results show that the co-current precooler provides favourable outlet heat sink temperatures but compromises compactness. For a similar technology level, the counter-current precooler yields excessive heat sink outlet temperatures due to a compact, robust, and efficient heat transfer design, but could be detrimental to precooler integrity due to corrosion, including the cycle performance, if not recirculated back into the sea effectively. For the counter-current, the ICR has the best heat sink average temperature ratio of 1.4; the SCR has 2.7 and IC has 3.3. The analyses aid the development of Gas Cooled Fast Reactors (GFRs) and Very High Temperature Reactors (VHTRs), where helium is used as the coolant.

Sensitivity of DynaWhirlpool hydrocyclone operation to applied back-pressure

The two-phase, air–water flow pattern in a DynaWhirlpool centrifugal separator is investigated using time-dependent, three-dimensional numerical simulation. The air–water interface is captured by the Volume-Of-Fluid approach, while the unresolved turbulence fluctuations are modeled via a second-order differential-stress turbulence model. Among the different operating variables, the back-pressure at the sink outlet affects significantly the flow within the cyclone. The modifications experienced by the flow field as the back-pressure is increased are documented and interpreted. The variation of relevant operating variables is also reported, as the split ratio and the Euler number characterizing the device. It is verified that for large values of the back-pressure the water flow through the sink is hindered and the air core disappears. The flow pattern is moderately altered when the cyclone is fed with a non-Newtonian fluid with the same viscosity as a real water/magnetite dense medium.

Carbapenemase-bearing Klebsiella spp. in sink drains: investigation into the potential advantage of copper pipes

Sink drains have long been known to harbour pathogenic bacteria and efforts such as heated sink traps have been made to control them. Sink outlet pipes have been implicated in outbreaks of infection by multi-resistant Klebsiella pneumoniae. To investigate whether a change to copper pipes might prevent cross-infection, sections of standard sink outlet pipe were left in containers of water to which multi-resistant human strains of K. pneumoniae had been added. Bacterial counts from the water of containers to which copper pipe had been added were lower than those from containers to which PVC (polyvinyl chloride) pipe had been added.

Technical and economic working domains of industrial heat pumps: Part 1 – Single stage vapour compression heat pumps

A large amount of operational and economic constraints limit the applicability of heat pumps operated with natural working fluids. The limitations are highly dependent on the integration of heat source and sink streams. An evaluation of feasible operating conditions was carried out considering the constraints of available refrigeration equipment and a requirement of a positive net present value of the investment. Six heat pump systems were considered, corresponding to an upper limit of the sink temperature of 120 °C. For each set of heat sink and source temperatures the best available technology was determined. The results showed that four different heat pump systems propose the best available technology at different parts of the complete domain. Ammonia systems presented the best available technology at low sink outlet temperature. At high temperature difference between sink in- and outlet, the transcritical R744 expands the working domain for low sink outlet temperatures.

Hot water cooled electronics: Exergy analysis and waste heat reuse feasibility

We report an experimental study on exergetically efficient electronics cooling using hot water as coolant. It is shown that water temperatures as high as 60°C are sufficient to cool microprocessors with over 90% first law (energy based) efficiency. The chip used in our experiment is kept at temperatures of 80°C or below so as not to exceed any allowable industrial specifications for maximum microprocessor chip temperature. The use of hot water as coolant will eliminate the requirement for chillers typically used in air-cooled data centers and, therefore, significantly reduce the power consumption. An exergy analysis shows that a six fold rise in second law (exergy based) efficiency is achieved by switching the water inlet temperature from 30°C to 60°C. The resulting high exergy at the heat sink outlet is a measure of the potential usefulness of the waste heat of data centers, thereby helping to design data centers with minimal carbon footprint. A new metric for the economic value of the recovered heat, based on costs for electricity and fossil fuels, heat recovery efficiency and an application specific utility function, is introduced to underscore the benefits of hot water cooling. This new concept shows that the economic value of the heat recovered from data centers can be much higher than its thermodynamic value.

Compact Thermal Model for the Transient Temperature Prediction of a Water-Cooled Microchip Module in Low Carbon Emission Computing

This article presents a compact computational model for the rapid determination of the junction temperature of a chip cooled with a heat sink, exploring the concept of hot water cooled electronics as a strategy to reduce the carbon footprint of data centers. The model aims at rapid simulations of variations of the chip, as well as the heat sink outlet water temperatures during transient heat loads. The model is validated by experimental tests with a water-cooled manifold microchannel (MMC) heat sink, which is designed to cool the processors of state-of-the-art servers. The chip temperature is determined subject to periodic heat loads as large as 100 W with frequencies in the range from 1 to 10 Hz. The results show that to calculate 1 s of real temperature variation requires less than 20 s of computational time on a Quad-Core AMD Opteron 2350, 2 GHz desktop PC with 4 GB RAM. The thermal response of the heat sink to real-time power traces with durations up to 200 s is modeled for different flow rates. The simulations indicate that application of a flow-control feedback loop could achieve more than 50% reduction in water flow rate, without compromising the maximal chip temperatures.

Analysis of a combined law power-optimized open Joule-Brayton heat-engine cycle with a finite interactive heat source

Through concurrent employment of the first and second laws of thermodynamics, a set of optimum power expressions for the open irreversible Brayton and open Joule-Brayton heat-engine cycles has been obtained. These expressions are applicable to configurations with a finite thermal reservoir in which the values of the source outlet temperatures are forced to interact with the overall cycle during the power optimization of the cycle's working substance temperatures. Use of the concurrent law procedure simultaneously allows both the minimization of internal cycle entropy generation and the maximization of specific cycle work in order to provide the internal cycle operating temperatures necessary for power optimization. The study is carried out for open versions of these cycles in which the energy input is provided from an external source through a heat exchanger, the conductance of which is optimally allocated with respect to the cycle flow rate. The work includes a novel comparative study of the optimized power output of these cycles both with non-interactive and with interactive sources. The results of this study conclusively indicate the importance of considering variable (interactive) sink outlet temperatures in obtaining the power optimum for these cycles.

97/05001 Economic analyses of absorption systems: part A—design and cost evaluation: Siddiqui, M. A. Energy Convers. Mgmt., 1997, 38, (9), 889–904

The eco-friendly zeotropic mixtures of R1233zd(E) with four hydrocarbons were investigated to replace the traditional refrigerants (R22 and R134a) in heat pump water heaters. Under the nominal working condition, the performances of heat pump were analyzed by establishing the mathematical model based on the fixed pinch point temperature difference in the heat exchangers. The results show that both blends R1233zd(E)/R1270 and R1233zd(E)/R290 are suitable drop-in candidates of R22 or R134a for heat pump water heaters. The R1233zd(E)/R1270 with optimal mass fraction 16%/84% demonstrates the best system COP which is respectively 2.13% and 10.14% higher than those of R22 and R134a. The temperature glide feature of zeotropic mixture influences on the system COP greatly in matching both heat transfer processes in condenser and evaporator. The heat sink outlet temperature influences the system COP greatly that when it is 45, 55 or 65 °C, the corresponding maximum system COP is 5.803, 4.646 or 3.888 with R1233zd(E)/R1270 and 5.724, 4.535 or 3.757 with R1233zd(E)/R290 respectively. Also, the optimal fraction of R1233zd(E) shifts to a slightly higher value with the rise of heat sink outlet temperature.