Cooling Tower Fan Speed Control Using Approach Temperature
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Solution Overview
Problem
Current cooling tower control systems face challenges in efficiently managing the number of operating cooling towers and fan output to maintain constant water temperatures, especially during varying equipment loads and seasonal changes, leading to high energy consumption and slow response times.
Innovation Solution
A cooling tower controlling system that adjusts the rotational speed of fans based on load periods, using a first and second approach temperature to control the difference between circulating water temperature and outside air wet-bulb temperature, allowing for dynamic fan operation and efficient energy use by anticipating load changes through feed-forward control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If inverter control is used to lower fan rotational speed when equipment load is low or outside air temperature is low, then electric power consumption is reduced, but cooling water temperature control precision deteriorates
Solution Approach 1:
The control system performs preliminary actions by switching between day-time and night-time control modes in advance based on predetermined timing. The night-time control mode prepares for potential temperature drops by maintaining higher fan speeds earlier, while the day-time control mode prepares for temperature rises. This preliminary switching prevents temperature deviations before they occur, resolving the contradiction between energy savings and temperature control precision.
Solution Approach 2:
The control system continuously monitors cooling water temperature and outside air temperature, using this feedback to dynamically adjust fan rotational speeds. When temperature deviations are detected, the system responds by adjusting fan speeds accordingly, ensuring precise temperature control while optimizing energy consumption based on actual conditions rather than fixed schedules.
2Use of energy by moving object
If fan rotational speed is reduced to save energy during low load periods, then electric power consumption is reduced, but response time to load changes increases
Solution Approach 1:
The control system dynamically adjusts fan rotational speeds based on real-time conditions rather than operating at fixed speeds. During night-time high-load periods, fans operate at higher speeds to ensure rapid response to cooling demands. During day-time low-load periods, fans operate at lower speeds to save energy. The system can quickly transition between these states when load changes occur, resolving the contradiction between energy savings and response time.
Solution Approach 2:
The control system switches control modes in advance based on predetermined timing (day-time/night-time periods). This preliminary switching ensures that fans are already at appropriate speeds before load changes occur, enabling rapid response when equipment load changes without requiring excessive energy consumption during transition periods.
3Temperature
If multiple cooling towers operate at high fan output to maintain water temperature during hot periods, then cooling water temperature is maintained, but electric power consumption increases
Solution Approach 1:
The control system applies different control strategies to different time periods (day-time vs. night-time modes) and different operational conditions. During day-time periods when outside air temperatures are high, the system accepts higher water temperatures to save energy. During night-time periods when outside air temperatures are low, the system prioritizes temperature control. This localized quality approach resolves the contradiction between temperature maintenance and energy consumption by optimizing for different conditions in different locations of the operational timeline.
Solution Approach 2:
The control system changes operational parameters (fan rotational speeds, control mode) based on outside air temperature and time of day. When outside air temperature is high during day-time, the system reduces fan speeds and accepts higher water temperatures. When outside air temperature drops at night-time, the system increases fan speeds to maintain lower temperatures. This parameter changes approach resolves the contradiction by adapting the system's temperature control strictness and energy consumption to match environmental conditions.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables effective temperature control of cooling water corresponding to equipment loads with reduced energy consumption and minimizes extreme water temperature gradients, improving response times and maintaining consistent cooling performance.
Implementation Method 1
a cooling fan, a rotation driving unit which is a driving source for rotating the cooling fan
Implementation Method 2
cooling water used for heat exchange with equipment
Data Source
AI summary
A cooling tower controlling system includes a plurality of cooling towers, a plurality of pumps, a circulation line through which circulating cooling water flows, a temperature measuring unit, a first load controlling unit, and a second load controlling unit. The temperature measuring unit measures a temperature TE1 of the circulating cooling water at a position upstream of a heat exchange unit and downstream of a storage unit. The first load controlling unit controls a rotational speed of the cooling fans so that an absolute value ΔTE of the difference between the temperature TE1 and an outside air wet-bulb temperature TE0 comes within a first approach temperature AP1 corresponding to a first load in a first load period. The second load controlling unit controls a rotational speed of the cooling fans so that the absolute value ΔTE of the difference between the temperature TE1 and the outside air wet-bulb temperature TE0 comes within a second approach temperature AP2 corresponding to a second load in a second load period.