Energy audit of condensation-type tumble washer-dryers in an Indian household: Performance analysis of drying cycles

Abstract

Washer-dryers have become indispensable in urban households, particularly in high-rise buildings where space constraints limit the use of separate appliances. With the growing adoption of washer-dryers and the emphasis on sustainable living, it is crucial to understand their performance characteristics to optimize energy efficiency and resource utilization. In this direction, an experimental energy audit was conducted to assess the drying performance of LG and IFB condensation-type washer-dryer units, focusing on two key performance metrics: Specific Moisture Extraction Rate (SMER) and Combined Energy Factor (CEF). Comprehensive temperature and relative humidity measurements at critical points in the drying loop provided insights into the heat and mass transfer process that govern drying phenomenon in two commercially-available condensation-type washer dryers.

The LG washer-dryer demonstrated superior energy efficiency of the two models tested, consistently achieving higher CEF values across all drying modes. The IFB unit reached a peak CEF of $\approx 10$ lb/kWh during shorter drying cycles (e.g., 1-hour cycles), while a significant drop in CEF was observed during longer cycles, such as cupboard dry mode lasting approximately 5 h. The SMER values for both units were similar, averaging $\approx 0.75\mathrm{kg/kWh}$, resulting in a comparable moisture extraction performance. At an average, IFB unit operated at temperature $\approx$ 25${}^{o}C$ higher than the LG unit with evidence of intelligent control mechanisms during extended drying leading to similar SMER value.

A physics-based thermodynamic model was used to estimate instantaneous moisture extraction rates from temperature and humidity data. The model revealed that a relative humidity difference of 40% was the primary driver of mass transfer. Model predictions for total water removal were found to be within 25% of experimental measurements, validating the thermodynamic framework. The study provides region-specific experimental data and performance benchmarking of electric heater-based washer-dryer units under high-humidity tropical conditions, a domain with limited existing literature. The findings establish a critical baseline for optimizing energy-efficient, cost-effective appliance designs suitable for emerging markets such as India.