Control of discharge dewpoint for packaged terminal air conditioner
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Solution Overview
Problem
Conventional packaged terminal air conditioners (PTACs) face issues with introducing humid outdoor make-up air, leading to uncomfortable indoor conditions and increased energy consumption due to continuous operation of refrigeration loops to manage humidity, without effective monitoring or adjustment of combined air quality.
Innovation Solution
An air conditioning unit with a refrigeration loop, evaporator, condenser, compressor, expansion device, indoor and auxiliary fans, and a controller that monitors dewpoint temperature and adjusts fan and compressor speeds to maintain desired air quality by combining indoor and outdoor air flows.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If outdoor make-up air is continuously drawn into the indoor space, then fresh air ventilation is provided to the indoor space, but unwanted humidity is introduced to the conditioned space
Solution Approach 1:
The system continuously monitors the dewpoint temperature of the combined air delivered to the conditioned space and uses this feedback to dynamically adjust the refrigeration loop operation, ensuring humidity is controlled while maintaining fresh air ventilation
Solution Approach 2:
The system adjusts the operating parameters of the refrigeration loop (such as compressor speed and refrigerant flow) based on the monitored dewpoint temperature, changing parameters dynamically to match the humidity content of the incoming make-up air
2Object-affected harmful factors
If the refrigeration loop continuously operates to manage humidity in humid make-up air, then humidity is controlled in the conditioned space, but electrical consumption increases
Solution Approach 1:
The system uses dewpoint temperature monitoring to determine when refrigeration is actually needed, allowing the refrigeration loop to operate only when humidity control is required rather than continuously, thereby reducing electrical consumption
Solution Approach 2:
The system transitions from static continuous operation to dynamic operation, adjusting the refrigeration loop activity based on real-time humidity conditions of the make-up air and actual needs of the conditioned space
3Object-affected harmful factors
If known solutions operate the refrigeration loop continuously when make-up air is provided, then humid make-up air is managed, but additional mechanical components and increased electrical consumption are required
Solution Approach 1:
The system uses the existing refrigeration loop for multiple purposes: both for cooling the conditioned space and for dehumidifying the make-up air, eliminating the need for separate dedicated dehumidification equipment
Solution Approach 2:
The system monitors its own output air quality and self-regulates the refrigeration loop operation accordingly, without requiring external control systems or additional mechanical components
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
Effectively regulates indoor air quality by controlling dewpoint temperature, ensuring comfortable conditions and reducing energy consumption by optimizing fan and compressor operation based on air quality feedback.
Implementation Method 1
an evaporator and a condenser
Implementation Method 2
a compressor operably coupled to the refrigeration loop and being configured to urge refrigerant through the refrigeration loop
Implementation Method 3
an evaporator and a condenser
Data Source
AI summary
A packaged terminal air conditioner unit includes discharge air temperature and humidity sensors in the discharge air stream. Input from the sensors is used to determine the dewpoint temperature of a mixture of outside air and recirculated room air prior to discharge to the conditioned space. The air conditioner unit modifies one or more of indoor fan speed, compressor speed, and an electronically controlled expansion device to adjust the discharge air dewpoint temperature to a predetermined target value.