Experimental analysis of a domestic electric hot water storage tank. Part II: dynamic mode of operation

Abstract

In this paper, the experimental analysis of a full-scale Domestic Electric Hot Water Storage Tank (DEHWST) with a capacity of 150 l is reported. The tank is equipped with three different inlets and two different outlets of practical interest. The dynamic mode of operation of the tank has been experimentally analyzed taking into account the six possible inlet-outlet port arrangements and water draw-off flow rates of 5, 10 and 15 l/min. The analysis is based on the transient temperature distributions of the outlet and inlet water flow and on the transient temperature profiles of the water inside the tank measured by an appropriate data acquisition system. Performance parameters to evaluate the thermal stratification in the tank and the discharging energy and exergy efficiencies are defined and calculated from the experimental data. The characteristic performance of the tank with different inlet-outlet port configurations is analyzed and the best one is identified and proposed to use in practice.

Improving the energy storage capability of hot water tanks through wall material specification

“…[22], the role of the Richardson's number, which expresses the ratio of potential to kinetic energy within stratified water, was identified. During 'dynamic mode operation', where hot water is drawn from the tank, stratification breaks down as flow rates increase and the Richardson's number drops [24], this can be observed in experiments where the vertical temperature distribution is monitored over time [25]. Increasing the tank's aspect ratio (height/diameter) reduces dynamic mode de-stratification at the expense of elevated heat losses [26] with an optimum value being somewhere between 3 and 4, a range confirmed experimentally in Ref.…”

Theoretical and experimental investigations of a two-phase thermosyphon solar water heater

“…Rosen et al [7] also used the same concept to study the thermodynamic performances of cold thermal storage systems. Besides, Fernandez-Seara et al [8] and Ragoonanan et al [9] employed the energy balance model to predict the charge and discharge capabilities of the thermal water heaters in transient-state. Ozturk [10] evaluated the overall efficiency of an underground solar thermal storage system.…”

Research of Operation Modes of Heat Storage Tank in CHP Plant Using Numerical Simulation

“…Stratification number is selected in this work. For the dynamic mode of operation, the stratification number is defined as the ratio of the mean of the temperature gradients at any time to the maximum mean temperature gradient for the discharging/charging process, according to this equation [8,17]: The average stratification number 0.913 was determined during the analysis. The high value of the stratification number shows a good fulfilment of design and operating conditions of the storage tank.…”

“…The mean maximum temperature gradient is obtained considering that the maximum temperature difference during the charging or discharging process is concentrated in only one of the water layers considered in this analysis; then the gradient in the remaining layers is zero [17].…”