System and terminal unit for conditioning of indoor air

Abstract

A system and terminal unit are provided for efficiently and effectively conditioning indoor air. Some embodiments address temperature control, humidity control, air quality control, while also introducing conditioned outdoor air. One aspect relates to a terminal unit that monitors and controls sensible and latent cooling rates to simultaneously meet temperature and humidity setpoints for the conditioned space. A sensor suite provides measurements for monitoring cooling rates and a control system controls actuators to meet the sensible and latent cooling requirements. The terminal unit may have a secondary recirculation air intake that bypasses the cooling coil to warm supply air prior to exiting the terminal unit. The terminal unit may be part of an air conditioning system where it is connected to a main branch of a hybrid branch controller which avoids having a home run to the HBC for each terminal unit.

What is claimed is: 
     
         1 . An air conditioning system comprising:
 a terminal unit having
 a mixing chamber; 
 a first recirculation air port for receiving first recirculation air and connected to the mixing chamber by a first duct; 
 a cooling coil within the first duct for cooling the first recirculation air; 
 a second recirculation air port for receiving second recirculation air and connected to the mixing chamber; 
 a conditioned air port for receiving conditioned air and connected to the mixing chamber; and 
 a supply air port for providing supply air and connected to the mixing chamber; 
   
       wherein the mixing chamber combines the first recirculation air, the second recirculation air, and the conditioned air to produce the supply air. 
     
     
         2 . The air conditioning system of  claim 1 , wherein the terminal unit is a first terminal unit, the system further comprising:
 a plurality of terminal units including the first terminal unit;   a hybrid branch controller having
 a pair of refrigerant pipe ports for receiving and returning refrigerant; 
 a pair of cold water pipe ports; and 
 a heat exchanger having refrigerant piping connected to the pair of refrigerant pipe ports and water piping connected to the pair of cold water pipe ports; and 
   piping connecting the plurality of terminal units to the pair of cold water ports.   
     
     
         3 . The air conditioning system of  claim 1 , wherein the supply air port of the terminal unit is connected to the mixing chamber by a second duct, the terminal unit further comprising:
 a fan within the second duct to draw air from the mixing chamber and blow the supply air through the supply air port.   
     
     
         4 . The air conditioning system of  claim 1 , wherein the terminal unit further comprises an actuator to control a flow rate of second recirculation air through the second recirculation air port. 
     
     
         5 . The air conditioning system of  claim 4 , wherein the actuator is a damper. 
     
     
         6 . The air conditioning system of  claim 4 , wherein the terminal unit further comprises:
 a temperature sensor to measure a temperature of the supply air; and   a controller to control the actuator based on the temperature of the supply air.   
     
     
         7 . The air conditioning system of  claim 6 , wherein the controller of the terminal unit is configured to adjust the actuator to control the flow rate of the second recirculation air, at least in part, in proportion to a difference between a threshold temperature and the temperature of the supply air if the temperature of the supply air is below the threshold temperature. 
     
     
         8 . The air conditioning system of  claim 7 , wherein the supply air port of the terminal unit is connected to the mixing chamber by a second duct, the terminal unit further comprising:
 a fan within the second duct to draw air from the mixing chamber and blow the supply air through the supply air port.   
     
     
         9 . An air conditioning system comprising:
 a hybrid branch controller having
 a pair of refrigerant pipe ports for receiving and returning refrigerant; 
 a pair of cold water pipe ports; and 
 a heat exchanger having refrigerant piping connected to the pair of refrigerant pipe ports and water piping connected to the pair of cold water pipe ports; 
   a plurality of terminal units; and   piping connecting the plurality of terminal units to the pair of cold water ports.   
     
     
         10 . The air conditioning system of  claim 9 , wherein at least one of the plurality of terminal units comprises:
 a mixing chamber;   a first recirculation air port for receiving first recirculation air and connected to the mixing chamber by a first duct;   a cooling coil within the first duct for cooling the first recirculation air;   a second recirculation air port for receiving second recirculation air and connected to the mixing chamber;   a conditioned air port for receiving conditioned air and connected to the mixing chamber; and   a supply air port for providing supply air and connected to the mixing chamber;   wherein the mixing chamber combines the first recirculation air, the second recirculation air, and the conditioned air.   
     
     
         11 . A terminal unit for conditioning the air of a conditioned space, the terminal unit comprising:
 a recirculation air port;   a conditioned air port;   a supply air port;   a mixing chamber connected to the recirculation air port via a recirculation air duct, the conditioned air port via a conditioned air duct, and the supply air port via a supply air duct;   a cooling coil in the recirculation air duct;   a first sensor in the supply air duct to measure a property of supply air passing through the supply air port;   a second sensor in the recirculation air duct to measure the property of recirculation air passing through the recirculation air port;   a controller configured to determine an amount of cooling being delivered to the conditioned space based at least in part on the property of the supply air and the property of the recirculation air measured by the first and second sensors, respectively, and to control coolant in the cooling coil based at least in part on the amount of cooling.   
     
     
         12 . The terminal unit of  claim 11 , wherein the recirculation air port is a first recirculation air port, the terminal unit further comprising:
 a second recirculation air port connected to the mixing chamber via a second recirculation air duct; and   a third sensor to measure the air flow rate through the second recirculation air port,   
       wherein the controller is configured to determine an amount of cooling based at least in part on the third sensor. 
     
     
         13 . The terminal unit of  claim 11 , further comprising:
 a fourth sensor to measure the property of conditioned air passing through the conditioned air port,   
       wherein the controller is further configured to determine an amount of cooling based at least in part on the property of the conditioned air measured by the fourth sensor. 
     
     
         14 . The terminal unit of  claim 11  further comprising a control valve operably connected to the cooling coil, wherein the controller controls the coolant in the cooling coil at least in part by modulating the control valve. 
     
     
         15 . The terminal unit of  claim 11 , wherein the amount of cooling is an amount of sensible cooling, the terminal unit further comprising:
 a fifth sensor in the recirculation air duct on the outlet side of the cooling coil to measure temperature of the recirculation air,   
       wherein
 the controller determines a recirculation air flow rate based at least in part from measurements from the first and second sensors, and 
 the controller determines the amount of sensible cooling based at least in part on a first amount of sensible cooling delivered by the cooling coil, the first amount of sensible cooling determined by the controller at least in part from measurement of the fifth sensor and the recirculation air flow rate. 
 
     
     
         16 . The terminal unit of  claim 15 , further comprising
 a sixth sensor in the conditioned air duct to measure temperature of conditioned air passing through the conditioned air port,   
       wherein determining the amount of sensible cooling the controller further determines a second amount of sensible cooling delivered by conditioned air passing through the conditioned air port, the second amount of sensible cooling determined by the controller at least in part from measurement of the sixth sensor. 
     
     
         17 . The terminal unit of  claim 11 , wherein the property is carbon dioxide concentration. 
     
     
         18 . The terminal unit of  claim 11 , wherein the controller is further configured to control a flow rate of recirculation air through the recirculation air port based at least in part on the property of the supply air and the property of the recirculation air. 
     
     
         19 . The terminal unit of  claim 11 , wherein the amount of cooling is an amount of latent cooling, the terminal unit further comprising:
 a seventh sensor in the recirculation air duct on the outlet side of the cooling coil to measure humidity of the recirculation air,   
       wherein
 the controller determines a recirculation air flow rate based at least in part from measurements from the first and second sensors, and 
 the controller determines the amount of latent cooling based at least in part on a first amount of latent cooling delivered by the cooling coil, the first amount of latent cooling determined by the controller at least in part from measurement of the seventh sensor and the recirculation air flow rate. 
 
     
     
         20 . The terminal unit of  claim 19 , further comprising
 an eighth sensor in the conditioned air duct to measure humidity of conditioned air passing through the conditioned air port,   
       wherein determining the amount of latent cooling the controller further determines a second amount of latent cooling delivered by conditioned air passing through the conditioned air port, the second amount of latent cooling determined by the controller at least in part from measurement of the eighth sensor.