viewparams.js

var felayer = new OpenLayers.Layer.WMS(
  name,
  MAPS_IMR_NO,
  {
    layers: "measurements_last_30_days",
    transparent: true,
    styles: style, 
    viewparams : 'type:'+typeValue
  },
  {
    isBaseLayer: false
  }
);
                   	 	
var getFeatureInfoController = Ext.ComponentMgr.all.find(function(c) {
  return c instanceof gxp.plugins.WMSGetFeatureInfo;
});
getFeatureInfoController.vendorParams= {viewparams : 'type:'+typeValue};
var r =  new record({layer: felayer, title: felayer.name}, felayer.id)
r.set('queryable', true);
mapPanel.layers.add(r);