A novel dual hot gas bypass defrosting (DHBD) method is developed to remove frost from the outside heat exchanger (HEX) of an air-to-air heat pump. The proposed method adopts two bypass lines of hot gas from the compressor: one is connected to the inlet of the outdoor HEX, and the other is...

ASFs (Annular stepped fins) require less material than ADFs (annular disc fins) while retaining the ability to produce the same cooling rate in a convection environment. A simple analysis was developed for ASFs that considered radiative heat transfer and heat generated by a nuclear reactor...

We report a novel defrosting control method for refrigeration systems including refrigerators and heat pumps that commonly use time control or time–temperature control to determine the defrosting start-time. However, these methods do not provide accurate defrosting start-times due to...

This study presents a simple approach to estimate the capacity of combined heat and power (CHP) units suitable for installation in high heat-to-power ratio (HPR) buildings when excess electricity cannot be sold back to the grid. The two different methods used in this approach, a graphical method...

Like dry surface fins, development of the boundary layer over a wet fin causes the heat transfer coefficient to vary over the fin surface. The present study analytically determines the performance of different fins geometries by analyzing the temperature-dependent thermal conductivity of the fin...

We report a LDC (load duration curve) method to determine the optimum size of CHP (combined heat and power) units. The method gives the appropriate capacity graphically from the LDC of a building's heating demand. The method can be applied to the most common CHP units that are connected to the...

A solely analytical method is investigated to determine the minimum fin shape of wet fins subject to variable heat transfer coefficients. The analysis is applicable to any surface condition, including dry, fully wet and partially wet. An optimization procedure based on the variational principle...

Light-emitting diode (LED) lighting offers greater energy efficiency than conventional lighting. However, if the heat from the LEDs is not properly dissipated, the lifespan and luminous efficiency are diminished. In the present study, a heat sink of LED lighting was optimized with respect to its...

The size of a cooling inventory is generally designed based on which size can endure the excessive heat load situations that occur sporadically. As a result, cooling systems are often too large for most normal driving modes. There have been numerous efforts to downsize the automotive engine...