Modelica Household Dishwater Model with External Heat Loop

With the United States being the world’s second largest consumer of primary energy, research into areas of significant consumption can provide large impacts in terms of the global energy consumption. Buildings account for 41% of U.S. total energy consumption with the residential sector making up a majority. Household appliances account for the second largest site energy consumption at 27%, after the HVAC system for the U.S. residential sector. Thermally integrating residential appliances by leveraging waste heat recovery goes outside U.S. federal standards and has not been adequately explored by connecting all residential appliances. Limited studies exist focused only on single appliances connected to waste heat recovery or being thermally integrated. As part of a thermally connected system, individual appliance models are developed in Modelica and are tuned with available experimental data from the manufacturer. The dishwasher (DW) has better opportunity as a heat sink to offset the internal heater, 0.17 kWh of electricity/cycle for heating wash water. Due to the integration approach required with the dishwasher, a detailed accounting of major components is required. The thermal mass of the DW cavity and dishware, the fluctuating flow rates of each spray arm, and the final water sump temperature required are all captured. After tuning, the DW model of the traditional system shows an agreement within ±5% for most water sump temperatures

Modelica Analysis of Thermally Connected Residential Appliances

With the United States being the world’s second largest consumer of primary energy, research into areas of significant consumption can provide large impacts in terms of the global energy consumption. Buildings account for 41% of U.S. total energy consumption with the residential sector making up a majority. Household appliances account for the second largest site energy consumption at 27%, after the HVAC system for the U.S. residential sector. Thermally integrating residential appliances by leveraging waste heat recovery goes outside U.S. federal standards and has not been adequately explored by connecting all residential appliances. Limited studies exist focused only on single appliances connected to waste heat recovery or being thermally integrated. Modelica appliance models have been developed for four household appliances: refrigerator-freezer (RF), dishwasher (DW), clothes dryer (CD), and clothes washer (CW). The Modelica models capture individual use and the predictions of the RF and DW were compared against available experimental data. The individual models have been connected to a simple storage tank model to simulate the integrated appliance system. Modelica predicts the energy savings under the integrated system and captures any impact from integration

Recovery of Waste Thermal Energy in U.S. Residential Appliances

With the United States being the world’s second largest consumer of primary energy, research into areas of significant consumption can provide large impacts in terms of the global energy consumption. Buildings account for 41% of US total energy consumption with the residential sector making up a majority. Household appliances account for the second largest site energy consumption at 27%, after the HVAC system for the U.S. residential sector. By quantifying the expected energy available in the waste stream for five major appliances; household refrigerator, clothes dryer and washer, dishwasher, and cooking oven, a potential energy source is presented. A cold water cooling stream is applied to the waste stream of each appliance and an estimated amount of energy can be recovered. The household refrigerator is modeled having an increase in cooling capacity of about 12% and a reduction on compressor power consumption of about 26%. A sample operation of the clothes dryer has the exhaust air stream being cooled down to 30.5°C (86.9°F) or on the other side, is able to heat 19 liter (5 gal) of water up to about 54.5°C (130.1°F). Large volumes of water are available by the clothes washer, but due to typical operation characteristics, low wash and rinse temperatures, the waste stream was not high in temperature. While the dishwasher provided higher heat source temperatures, 40°C (104°F), than the clothes washer, 36°C (97°F), the opposite was true. The volume of waste water drained is very low compared to the clothes washer 11.7 liter (3.1 gal) to 155 liter (41 gal). Thus water temperatures in the storage tank did not reach above 30°C (86°F) even with low storage volumes. The cooking oven can generate very high water temperatures depending how small of a storage tank is connected. Further work in this area is recommended due to the potential of high water temperatures generated from residential waste energy streams not currently being captured, and thus can offset some site-energy usage

Waste heat recovery from a vented electric clothes dryer utilizing a finned-tube heat exchanger

Conventional residential clothes dryers continuously vent moist, hot air during the drying process. The vented air leaves the home but still has useful temperature and humidity that could be recovered to offset other heating demands in the home. A study is carried out to quantify the amount of heat extracted from the waste heat stream of a conventional, vented clothes dryer. To extract the heat, a water cooled, fin-and-tube heat exchanger is located within the exhaust duct. A steady state thermodynamic dry coil and wet coil model was built in Engineering Equation Solver (EES). The model accounts for the heat exchangers geometry and applies a dimensionless heat and mass transfer analogy (Colburn-j-factor) determined empirically to calculate an overall heat transfer coefficient for both dry and wet areas of the coil. Assuming water and moist air inlet temperatures and air and water side flow rates, a rate of heat transfer and outlet temperatures of both streams are predicted. Comparing the model prediction to experimental results identifies the accuracy of the model. Using energy balance, the potential heat available and the heat recovered are calculated and the effectiveness of the finned-and-tube heat exchanger are determined. It was observed that approximately 0.1 kWh of energy was recovered leading to a heat exchanges effectiveness of 55%

Energy Simulation And Optimized Retrofit Practices Applied To A Real Dwelling

Energy simulation and optimized retrofit practices applied to a real dwelling Giulia Marinello(a), Stephen L. Caskey(a), Eric J. Bowler(b), and Eckhard A. Groll(a) (a) Purdue University, School of Mechanical Engineering, ?Ray W. Herrick Laboratories, West Lafayette, IN 47907, USA (b)Whirlpool Corporation, Benton Harbor, MI 49022, USA Abstract According to the US Environmental Protection Agency, residential housing units account for 20.9% of the total energy usage in the U.S., causing 20.8% of the nation’s total carbon dioxide emissions. The average age of a single family home in the US is 34 years. These aging dwellings were built in a time when energy was cheap and carbon dioxide emission was not considered pollution. Therefore, these houses typically do not contain many energy efficiency measures. The practice of house retrofitting represents a huge source of energy saving. Although there are some general fundamental rules on how to retrofit a house, many different improvements can be applied and the optimum solution is normally based on the previous conditions of the house and on the climate zone where the house is located. In the past few years, many, increasingly sophisticated, software solutions able to provide energy modeling of a residential building have been developed. In this paper, a typical 1950s vintage residential house located in West Lafayette, Indiana, is taken as a case study. The aim is to combine the results obtained from two different energy simulation engines and compare them with real time energy usage data before and after the retrofit. The software tools used are BEOpt and Ecotect. BEOpt was developed by the National Renewable Energy Laboratory and is able to run optimization analyses and provide an indication on the most cost-effective improvements that can be done. Ecotect is based on Autodesk and is able to provide a more accurate energy analysis based on a 3D model of the house developed in Revit. The aim is to run an optimization analysis with BEOpt to identify the best retrofit practices for the case study and use the results to run a more accurate energy analysis in Ecotect. The results of the energy simulation can then be compared with real data thanks to the instrumentation system installed in the aforementioned house. The parameters monitored are the electricity consumption of every circuit, gas consumption, water consumption, and water temperature after the usage. Data from the house will be stored for a year to create a baseline scenario. The suggestions given by the energy simulation will be used to inform actual retrofit actions, which will be put in place during the summer of 2014. This study is part of a larger research project called the NEWW House, a collaboration between Whirlpool Corporation and Purdue University. The overall goal is to retrofit the residential building in order to create a net-zero energy and water house

Simulation of an Air-Source Heat Pump with Two-Stage Compression and Economizing for Cold Climates

A new air-source heat pump technology optimized for cold climates was designed and fabricated by the authors in close cooperation with three industrial partners. The constructed unit will undergo a field demonstration in a military barrack to identify heat pumps as cost effective systems that have less primary energy consumption when compared to traditional cold climate heating methods. A simulation model developed in EES predicted the designed heat pump performance at different ambient conditions. The EES results were incorporated with a TRNSYS model to couple the military barrack building load with the available heat pump capacity using weather data. The TRNSYS model enables the assessment of the field demonstration performance during the heating season. The heat pump design is based on two-stage compression with economizing. Commercially available components were selected for all parts of the heat pump. A variable-speed scroll compressor is used as the high-stage compressor matched with a tandem fixed-speed scroll compressor used as the low-stage compressor. The configuration has a predicted capacity of 18.34 kW (62,580 BTU/h) at the design ambient temperature of -20oC (4oF) based on the EES simulation results. The building has a heating load of less than 18 kW for more than 95% of the heating season that lasts 8 months out of the year. The heat pump design therefore is predicted to satisfy the building heating load for the entire heating season. The heating season COP based on TRNSYS hourly simulation results is 3.67 with a yearly heating capacity of 30,970 kWh (105,674 kBTU) and 8,438.37 kWh (28,793 kBTU). The CCHP simulations predict over 30% savings in primary energy and CO2 emissions with a 25% cost savings for annual heating energy use compared to an 85% AFUE natural gas furnace

Experimentally Observed Anomalies from Inclining a Vapor Compression Cycle

Vapor compression cycles would have many applications in the space industry if it was not for the uncertainty imposed by microgravity environments on two-phase systems. A first step towards Zero-G for technologies involving fluid dynamics can be terrestrial testing at different orientations. For vapor compression cycles, there is very little literature describing this type of research. This paper describes the anomalies encountered during the pursuit of a continuous operation of a R134a vapor compression cycle while positioning it at fixed angles around one axis between 0 and 360°. Experimental data was collected on a dedicated test stand across two configurations, one using a flat-plate evaporator and the other configuration using a tube-in-tube evaporator. Liquid flooding of the suction line was observed for both configurations but also continuous operation throughout a complete loop for certain cycle conditions. Charge migration towards the evaporator when it was put at the bottom was calculated based on differing measurements of the two mass flow meters in the liquid and suction line

Characterizing Steady State Compressor Performance by Using Transient Test Data

Compressor testing is an essential task to characterize compressor performance, but often requires significant time to be executed. This study suggests a method that could greatly reduce time needed for compressor testing by inferring steady state performance from transient data rather than waiting for true steady state conditions to be measured. The key finding is that the overall isentropic efficiency in transient operation is almost identical to its true steady state performance value after applying very simple data processing. The paper describes a simple data processing method that extracts steady-state performance from transient data. The proposed processing should not be understood as a general rule to all compressors, but as a positive result for this particular compressor and a first glimpse into the value of transient data for performance estimation