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Title: Affordable Hybrid Heat Pump Clothes Dryer

Abstract

This project was successful in demonstrating the feasibility of a step change in residential clothes dryer energy efficiency by demonstrating heat pump technology capable of 50% energy savings over conventional standard-size electric dryers with comparable drying times. A prototype system was designed from off-the-shelf components that can meet the project’s efficiency goals and are affordable. An experimental prototype system was built based on the design that reached 50% energy savings. Improvements have been identified that will reduce drying times of over 60 minutes to reach the goal of 40 minutes. Nevertheless, the prototype represents a step change in efficiency over heat pump dryers recently introduced to the U.S. market, with 30% improvement in energy efficiency at comparable drying times.

Authors:
 [1];  [2];  [1];  [2]
  1. Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
  2. Jabil, St. Petersburg, FL (United States)
Publication Date:
Research Org.:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1282484
Report Number(s):
PNNL-25510
400480000
DOE Contract Number:
AC05-76RL01830
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATION

Citation Formats

TeGrotenhuis, Ward E., Butterfield, Andrew, Caldwell, Dustin D., and Crook, Alexander. Affordable Hybrid Heat Pump Clothes Dryer. United States: N. p., 2016. Web. doi:10.2172/1282484.
TeGrotenhuis, Ward E., Butterfield, Andrew, Caldwell, Dustin D., & Crook, Alexander. Affordable Hybrid Heat Pump Clothes Dryer. United States. doi:10.2172/1282484.
TeGrotenhuis, Ward E., Butterfield, Andrew, Caldwell, Dustin D., and Crook, Alexander. 2016. "Affordable Hybrid Heat Pump Clothes Dryer". United States. doi:10.2172/1282484. https://www.osti.gov/servlets/purl/1282484.
@article{osti_1282484,
title = {Affordable Hybrid Heat Pump Clothes Dryer},
author = {TeGrotenhuis, Ward E. and Butterfield, Andrew and Caldwell, Dustin D. and Crook, Alexander},
abstractNote = {This project was successful in demonstrating the feasibility of a step change in residential clothes dryer energy efficiency by demonstrating heat pump technology capable of 50% energy savings over conventional standard-size electric dryers with comparable drying times. A prototype system was designed from off-the-shelf components that can meet the project’s efficiency goals and are affordable. An experimental prototype system was built based on the design that reached 50% energy savings. Improvements have been identified that will reduce drying times of over 60 minutes to reach the goal of 40 minutes. Nevertheless, the prototype represents a step change in efficiency over heat pump dryers recently introduced to the U.S. market, with 30% improvement in energy efficiency at comparable drying times.},
doi = {10.2172/1282484},
journal = {},
number = ,
volume = ,
place = {United States},
year = 2016,
month = 6
}

Technical Report:

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  • The integration of a heat pump heat source into a clothes dryer has been investigated by several U.S. and foreign appliance developers and manufacturers but no commercial or residential heat pump clothes dryers are currently available in North America. The objectives of this effort were to: (1) Evaluate a heat pump dryer prototype relative to residential dryer performance tests. (2) Quantify the product limitations. (3) Suggest design changes that would reduce the impact of the limitations or that have a positive impact on the benefits. (4) Position the product relative to utility DSM/IRP opportunities (e.g., reduced connected load, or energymore » conservation). (5) Develop preliminary cost data The program evaluated the performance of a prototype closed-cycle heat pump clothes dryer designed and built by the Nyle Corporation. The prototype design goals were: (1) Drying times equivalent to a conventional electric clothes dryer. (2) 60% reduction in energy consumption. (3) Effective lint removal (to prevent coil fouling). (4) Cool-down mode performance similar to conventional dryer. (5) 20 lb load capacity. (6) Low temperature dry for reduced clothes wrinkle. Test results indicated that the closed-cycle heat pump met some of the above mentioned goals but it fell short with respect to energy savings and dry time. Performance improvement recommendations were developed for the closed-cycle dryer approach. In addition, the closed-cycle design potential was compared to an open-cycle heat pump dryer configuration.« less
  • Computational modeling is used to design a hybrid heat pump clothes dryer capable of saving 50% of the energy used by residential clothes dryers with comparable drying times. The model represents the various stages of a drying cycle from warm-up through constant drying rate and falling drying rate phases and finishing with a cooldown phase. The model is fit to data acquired from a U.S. commercial standard vented electric dryer, and when a hybrid heat pump system is added, the energy factor increases from 3.0 lbs/kWh to 5.7-6.0 lbs/kWh, depending on the increase in blower motor power. The hybrid heatmore » pump system is designed from off-the-shelf components and includes a recuperative heat exchanger, an electric element, and an R-134a vapor compression heat pump. Parametric studies of element power and heating element use show a trade-off between energy savings and cycle time. Results show a step-change in energy savings from heat pump dryers currently marketed in the U.S. based on performance represented by Enery Star from standardized DOE testing.« less
  • This study was undertaken to determine the suitability of using a southeastern home attic as a means of reducing the energy consumption of an electric clothes dryer. An inexpensive duct (duplicable for $25) was constructed to collect hot attic air from the peak of a south facing roof and introduce it into the dryer inlet. Instrumentation was added to measure inlet temperatures and operating time/energy consumption of the dryer. Standardized test loads, in addition to normal laundry, were observed over the period of one year. The heat-on time of the dryer tested was shown to be reduced .16 to .35more » minutes per /sup 0/C rise in inlet temperature. Inlet temperatures produced by the attic duct peaked at 56/sup 0/C(133/sup 9/F) in May/June and 40/sup 0/C(104/sup 0/F) in February. Based on peak temperatures available between 2 and 4 pm each month, a potential 20% yearly average savings could be realized. Economic viability of the system, dependant primarily on dryer usage, can be computed using a formula derived from the test results and included in the report.« less
  • The first project investigated the technical possibilities of adapting a domestic electric clothes dryer to utilize solar-heated water as the heat source, replacing electric resistance heat. The second project attempted to extract wastewater heat from a commercial dishwasher to preheat fresh water to be used in the next dish washing cycle. It is felt that the clothes dryer project has met all of intended goals. Although a solar application has some real-world practical problems, the application of a dryer connected directly to the home heating system will prove to be cost-beneficial over the life of a dryer. The additional costmore » of a heat exchanger is not excessive, and the installation cost, if installed with the initial house plumbing is less than $100. From a practical point of view, the complexity of installing a wastewater heat extracter is considered impractical. The environment in which such equipment must operate is difficult at best, and most restaurants prefer to maintain as simple an operation as possible. If problems were to occur in this type of equipment, the kitchen would effectively be crippled. In conclusion, further research in the concept is not recommended. Recent advances in commercial dishwashers have also considerably reduced the heat losses which accompanied equipment only a few years old.« less
  • A heat pump clothes dryer (HPCD) is an innovative appliance that uses a vapor compression system to dry clothes. Air circulates in a closed loop through the drum, so no vent is required. The condenser heats air to evaporate moisture out of the clothes, and the evaporator condenses water out of the air stream. As a result, the HPCD can achieve 50% energy savings compared to a conventional electric resistance dryer. We developed a physics-based, quasi-steady-state HPCD system model with detailed heat exchanger and compressor models. In a novel approach, we applied a heat and mass transfer effectiveness model tomore » simulate the drying process of the clothes load in the drum. The system model is able to simulate the inherently transient HPCD drying process, to size components, and to reveal trends in key variables (e.g. compressor discharge temperature, power consumption, required drying time, etc.) The system model was calibrated using experimental data on a prototype HPCD. In the paper, the modeling method is introduced, and the model predictions are compared with experimental data measured on a prototype HPCD.« less