A process control apparatus , comprising: a housing ; a process control device disposed in the housing; and a temperature control device operably coupled to the housing for regulating a temperature of an atmosphere internal to the housing , the temperature control device comprising a vortex tube and a flow control valve , the vortex tube having a vortex inlet for receiving a compressed fluid, a first vortex outlet for discharging fluid from the vortex tube at a first temperature, and a second vortex outlet for discharging fluid from the vortex tube at a second temperature that is higher than the first temperature, characterised in that the apparatus further comprises: the flow control valve coupled to the vortex tube to selectively direct the flow of fluid from the first and second vortex outlets of the vortex tube, the flow control valve comprising: a valve body defining a valve cavity , a first valve inlet in communication with the valve cavity and the first vortex outlet of the vortex tube, a second valve inlet in communication with the valve cavity and the second vortex outlet of the vortex tube, a first valve outlet in communication with the valve cavity and an atmosphere external to the housing , and a second valve outlet in communication with the valve cavity and the atmosphere internal to the housing; and a movable control element disposed in the valve cavity for selectively controlling the flow of fluid from the first and second vortex outlets and the atmosphere internal to the housing . a housing ; a process control device disposed in the housing; and a temperature control device operably coupled to the housing for regulating a temperature of an atmosphere internal to the housing , the temperature control device comprising a vortex tube and a flow control valve , the vortex tube having a vortex inlet for receiving a compressed fluid, a first vortex outlet for discharging fluid from the vortex tube at a first temperature, and a second vortex outlet for discharging fluid from the vortex tube at a second temperature that is higher than the first temperature, characterised in that the apparatus further comprises: the flow control valve coupled to the vortex tube to selectively direct the flow of fluid from the first and second vortex outlets of the vortex tube, the flow control valve comprising: a valve body defining a valve cavity , a first valve inlet in communication with the valve cavity and the first vortex outlet of the vortex tube, a second valve inlet in communication with the valve cavity and the second vortex outlet of the vortex tube, a first valve outlet in communication with the valve cavity and an atmosphere external to the housing , and a second valve outlet in communication with the valve cavity and the atmosphere internal to the housing; and a movable control element disposed in the valve cavity for selectively controlling the flow of fluid from the first and second vortex outlets and the atmosphere internal to the housing . a valve body defining a valve cavity , a first valve inlet in communication with the valve cavity and the first vortex outlet of the vortex tube, a second valve inlet in communication with the valve cavity and the second vortex outlet of the vortex tube, a first valve outlet in communication with the valve cavity and an atmosphere external to the housing , and a second valve outlet in communication with the valve cavity and the atmosphere internal to the housing; and a movable control element disposed in the valve cavity for selectively controlling the flow of fluid from the first and second vortex outlets and the atmosphere internal to the housing . <EOS>