The Maximum Potential Energy Savings from Optimizing Cold Deck and Hot Deck Reset Schedules for Dual Duct VAV Systems

1999 ◽  
Vol 121 (3) ◽  
pp. 171-175 ◽  
Author(s):  
Mingsheng Liu ◽  
David E. Claridge

This paper presents the physical models for the maximum potential thermal energy savings from optimizing the hot deck and cold deck reset schedules for dual duct variable air volume systems. The maximum potential savings can be determined by using these models combined with basic system operating parameters and bin data. The system performance can be evaluated by comparing the actual savings with the maximum potential savings. The energy savings from optimal cold deck and hot deck reset schedules in multi-zone buildings should be at least 75 percent of the maximum potential savings.

2019 ◽  
Vol 40 (6) ◽  
pp. 698-713
Author(s):  
Kok Haw Kong ◽  
Wen Tong Chong

In hot and humid tropical countries, the air-conditioning system has a high energy usage in commercial buildings. This study introduces a static balance duct design method for a temperature dependent variable air volume system. Ducts are looped together, which cause the air to self-balance and minimize the pressure loss across the duct network. The static balance duct network can easily identify the critical zone of highest pressure loss. This zone appears at the longest duct length from the air source and is always consistent for different load conditions. The air supplied to this critical zone is controlled by the zone temperature sensor, which directs feedback to the variable frequency drive fan of the air-handling unit. The rest of the variable air volume terminal units are zone temperature controlled. The duct looping design mitigates the problems in pressure variations and complements the temperature dependent control strategy. An open office case study is carried out to demonstrate the merit of the static balance duct design method. An actual installation was completed in a shopping mall. The recorded temperature readings verified that the static balance duct network and temperature dependent variable air volume air-conditioning system is operational and functional. Approximately 27% energy savings is achieved compared to the constant air volume system. Practical application: The static balance duct design method is a combination of equal friction duct design method and a loop duct network. This static balance duct network can identify the critical zone of highest pressure loss and this zone is always consistent. In this temperature-dependent variable air volume (TDVAV), the variable air volume (VAV) terminal unit at the critical zone is eliminated. The zone temperature sensor at the critical zone provides direct feedback to the variable frequency drive fan. All other terminal units are temperature dependent. The static balance TDVAV system enhances energy savings, improves the performance of VAV system and reduces the faults for VAV systems.


2011 ◽  
Vol 32 (4) ◽  
pp. 345-360 ◽  
Author(s):  
MH Kim ◽  
JH Kim ◽  
OH Kwon ◽  
AS Choi ◽  
JW Jeong

This study aims to present the fundamentals in which operation of a 100% outdoor air system integrates with indirect and direct evaporative cooling systems and to estimate its energy saving potential. The simulation of the proposed system is performed using a commercial equation solver program, and the annual operation energy saving potential with respect to a conventional variable air volume system is determined. This paper shows that significant operation energy savings (i.e. 21–51% less energy consumption) is possible principally by the pre-conditioning of supply air due to the waste heat recovery using the indirect evaporative cooler and the sensible heat exchanger units. By components, the proposed system shows a 16–25% less annual cooling coil load and an 80–87% reduced annual heating coil load with respect to the conventional variable air volume system, while there is no fan energy savings expected. Practical applications: This paper provides practical insight on how the evaporative cooling based 100% outdoor air system operates and how each essential component, such as the indirect evaporative cooler, cooling coil, direct evaporative cooler, heating coil and sensible heat exchanger should be controlled during the seasons for realising energy conservation benefits. The sequence of operation presented in this paper can be implemented to actual control logic.


2018 ◽  
Vol 174 ◽  
pp. 513-526 ◽  
Author(s):  
A. González-Gil ◽  
J.L. López-González ◽  
M. Fernández ◽  
P. Eguía ◽  
A. Erkoreka ◽  
...  

Author(s):  
Lei Zhao ◽  
Ting Wang

Petroleum coke is processed into calcined coke in a rotary kiln, where the temperature profiles of flue gas and coke bed are highly nonuniform due to different flow and combustion mechanisms. Motivated by saving energy costs, the effect of refractory brick’s thermal properties on potential energy savings is investigated. This study focuses on investigating potential energy savings by replacing inner one third of existing bricks with higher thermal capacity (Cp) and/or higher thermal conductivity (k) bricks. This investigation is motivated by postulating that the bricks with higher thermal capacity can store more thermal energy during the period of contacting with the hot gas and release more heat to the cock bed when the bricks rotate to below and in contact with the coke bed. A rotational, transient marching conduction numerical simulation is conducted using the commercial software FLUENT. The impact of brick heat capacity and thermal conductivity on transporting thermal energy to the coke bed is analyzed. The results show: (a) Increasing the heat capacity of brick layer reduces brick temperature which helps increase the heat transfer between the hot gas and brick, in other words it does help brick store more heat from the hot gas, but, heat transfer between brick and coke is reduced, which is opposite to the original postulation. (b) Higher brick thermal conductivity decreases brick temperature thus increases heat transfer between hot gas and the brick layer. The heat transfer from brick to coke bed is also increased, but not significantly. (c) Usually a brick with a higher Cp value also has a higher k-value. Simulation of a brick layer with both four times higher Cp and k values actually show appreciable heat is transported from the brick to the coke bed for one rotation for both lower and higher Cp and k bricks. The difference is not significant.


Author(s):  
Aaron P. Wemhoff ◽  
William Flaherty

Heating, ventilating, and air conditioning (HVAC) systems comprise a significant portion of U. S. energy consumption. A supervisory control approach allows for the reduction of HVAC energy used. The authors previously developed and discussed the Master Controller (MC) method as a type of supervisory control that minimizes HVAC energy consumption for a given system. This paper provides two advancements towards the application of the MC method in a real system. First, airflow constraints are incorporated into the MC algorithm. Second, an approach is developed for incorporating transient system loads that are calculated via commercial software. The constrained MC method is shown to produce energy savings of approximately 40% compared to a traditional Variable Air Volume (VAV) method and VAV method with chiller control for reducing HVAC energy consumption for an example system.


Author(s):  
Mingsheng Liu ◽  
Jinrong Wang

Abstract The coupled control unit is widely used in hotels, dormitory buildings, hospitals, and office buildings. Computer simulation models are developed to analyze the thermal energy performance of the coupled control units. Simulation results indicate that excessive airflow significantly increases thermal and fan power consumption. The variable air volume technique or the return air by-pass can be used to improve the energy performance of the coupled control units. The humidistat should be properly set and located to avoid excessive thermal energy consumption.


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