agid])) { foreach ($g_flag_thread[$flagid] as &$val) { flag_thread_filter($val); } flag_thread_set($flagid, $g_flag_thread[$flagid]); } } return $g_flag_thread[$flagid]; } // 设置缓存 $key = flagid / $val = flagid下tid数组 function flag_thread_set($key, $val) { global $g_flag_thread; FALSE === $g_flag_thread and $g_flag_thread = website_get('flag_thread'); empty($g_flag_thread) and $g_flag_thread = array(); $g_flag_thread[$key] = $val; return website_set('flag_thread', $g_flag_thread); } // 删除flag下tid缓存 function flag_thread_delete_cache($flagid) { global $g_flag_thread; FALSE === $g_flag_thread and $g_flag_thread = website_get('flag_thread'); empty($g_flag_thread) and $g_flag_thread = array(); if (isset($g_flag_thread[$flagid])) { unset($g_flag_thread[$flagid]); website_set('flag_thread', $g_flag_thread); } return TRUE; } // Delete by tid / 通过tid删除flag下的主题和对应flagid缓存 function flag_thread_delete_by_tid($tid) { global $g_flag_thread; FALSE === $g_flag_thread and $g_flag_thread = website_get('flag_thread'); if (empty($g_flag_thread)) { $g_flag_thread = array(); } else { $thread = well_thread_read_cache($tid); $arrlist = flag_thread_find($tid, 1, $thread['flags']); $flagarr = $ids = array(); foreach ($arrlist as $val) { $flagarr[] = $val['flagid']; $ids[] = $val['id']; if (isset($g_flag_thread[$val['flagid']])) unset($g_flag_thread[$val['flagid']]); } website_set('flag_thread', $g_flag_thread); // 主键更新 flag_update($flagarr, array('count-' => 1)); // 主键删除 flag_thread_delete($ids); } return TRUE; } // 主键删除 通过$flagid删除flag下的主题和对应flagid缓存 function flag_thread_delete_by_flagid($flagid) { global $g_flag_thread; FALSE === $g_flag_thread and $g_flag_thread = website_get('flag_thread'); $read = flag_read_cache($flagid); if (empty($read)) return TRUE; $arrlist = flag_thread_find_by_flagid($flagid, 1, $read['count']); if (empty($arrlist)) return TRUE; $flagarr = $ids = array(); $n = 0; foreach ($arrlist as $val) { ++$n; $flagarr[] = $val['flagid']; $ids[] = $val['id']; if (isset($g_flag_thread[$flagid])) unset($g_flag_thread[$flagid]); } website_set('flag_thread', $g_flag_thread); // 主键更新 flag_update($flagarr, array('count-' => $n)); // 主键删除 $r = flag_thread_delete($ids); return $r; } ?>组保留的标签 余下为需要删除的标签 unset($oldtag[$key]); } } } if (!empty($oldtag)) { $tagids = array(); foreach ($oldtag as $tagid => $tagname) { $tagids[] = $tagid; } well_oldtag_delete($tagids, $tid); } $r = well_tag_process($tid, $fid, $create_tag, $tagarr); return $r; } // 删除标签和绑定的主题 function well_oldtag_delete($tagids, $tid) { $pagesize = count($tagids); $arrlist = well_tag_find_by_tagids($tagids, 1, $pagesize); $delete_tagids = array(); // 删除 $tagids = array(); $n = 0; foreach ($arrlist as $val) { ++$n; if (1 == $val['count']) { // 只有一个主题 $delete_tagids[] = $val['tagid']; } else { $tagids[] = $val['tagid']; } } !empty($delete_tagids) and well_tag_delete($delete_tagids); $arlist = well_tag_thread_find_by_tid($tid, 1, $n); if ($arlist) { $ids = array(); foreach ($arlist as $val) $ids[] = $val['id']; well_tag_thread_delete($ids); } !empty($tagids) and well_tag_update($tagids, array('count-' => 1)); } // 标签数据处理 $arr=新提交的数组 $tagarr=保留的旧标签 function well_tag_process($tid, $fid, $new_tags = array(), $tagarr = array()) { if (empty($tid)) return ''; // 新标签处理入库 if ($new_tags) { $threadarr = array(); $tagids = array(); $i = 0; $size = 5; $n = count($tagarr); $n = $n > $size ? $size : $size - $n; foreach ($new_tags as $name) { ++$i; $name = trim($name); $name = stripslashes($name); $name = strip_tags($name); $name = str_replace(array(' ', '#', "@", "$", "%", "^", '&', '·', '<', '>', '；', '`', '~', '!', '￥', '……', ';', '?', '？', '-', '—', '_', '=', '+', '.', '{', '}', '|', ':', '：', '、', '/', '。', '[', ']', '【', '】', '‘', ' ', ' ', ' ', ' ', ' '), '', $name); $name = htmlspecialchars($name, ENT_QUOTES); if ($name && $i <= $n) { // 查询标签 $read = well_tag_read_name($name); if ($read) { // 存在 count+1 $tagids[] = $read['tagid']; } else { // 入库 $arr = array('name' => $name, 'count' => 1); $tagid = well_tag_create($arr); FALSE === $tagid and message(-1, lang('create_failed')); $read = array('tagid' => $tagid, 'name' => $name); } $tag_thread = array('tagid' => $read['tagid'], 'tid' => $tid); $threadarr[] = $tag_thread; $tagarr[$read['tagid']] = $read['name']; } } !empty($threadarr) and tag_thread_big_insert($threadarr); !empty($tagids) and well_tag_update($tagids, array('count+' => 1)); } $json = empty($tagarr) ? '' : xn_json_encode($tagarr); return $json; } ?>内容的栏目 * @param int $category 0列表 1频道 2单页 3外链 * @return array */ function category_list($forumlist, $model = 0, $display = 0, $category = 0) { if (empty($forumlist)) return NULL; static $cache = array(); $key = $model . '-' . $display . '-' . $category; if (isset($cache[$key])) return $cache[$key]; if ($display) { foreach ($forumlist as $k => $val) { if (1 == $val['display'] && 1 == $val['type'] && $val['category'] == $category) { $cache[$key][$k] = $val; } } } else { foreach ($forumlist as $k => $val) { if (1 == $val['type'] && $val['category'] == $category) { $cache[$key][$k] = $val; } } } return empty($cache[$key]) ? NULL : $cache[$key]; } /** * @param $forumlist 所有版块列表 不分模型 * @param int $display 0全部CMS栏目 1在首页和频道显示内容的栏目 * @param int $category 0列表 1频道 2单页 3外链 * @return array */ function category_list_show($forumlist, $display = 0, $category = 0) { if (empty($forumlist)) return NULL; static $cache = array(); $key = $display . '-' . $category; if (isset($cache[$key])) return $cache[$key]; if ($display) { foreach ($forumlist as $k => $val) { if (1 == $val['display'] && 1 == $val['type'] && $val['category'] == $category) { $cache[$key][$k] = $val; } } } else { foreach ($forumlist as $k => $val) { if (1 == $val['type'] && $val['category'] == $category) { $cache[$key][$k] = $val; } } } return empty($cache[$key]) ? NULL : $cache[$key]; } /** * @param $forumlist 所有版块列表 * @return mixed BBS栏目数据(仅列表) 尚未开放bbs频道功能 */ function forum_list($forumlist) { if (empty($forumlist)) return array(); static $cache = array(); if (isset($cache['bbs_forum_list'])) return $cache['bbs_forum_list']; $cache['bbs_forum_list'] = array(); foreach ($forumlist as $_fid => $_forum) { if ($_forum['type']) continue; $cache['bbs_forum_list'][$_fid] = $_forum; } return $cache['bbs_forum_list']; } // 导航显示的版块 function nav_list($forumlist) { if (empty($forumlist)) return NULL; static $cache = array(); if (isset($cache['nav_list'])) return $cache['nav_list']; foreach ($forumlist as $fid => $forum) { if (0 == $forum['nav_display']) { unset($forumlist[$fid]); } } return $cache['nav_list'] = $forumlist; } ?>缺氟为什么会结霜
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缺氟为什么会结霜

2025-06-09 22:51:23   0次

缺氟为什么会结霜

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制冷系统缺氟会导致蒸发压力下降，使蒸发器局部温度过低，空气中的水蒸气在低温表面凝结成霜。具体表现为膨胀阀附近先结霜，随后逐渐蔓延至整个蒸发器和回气管。这是因为缺氟时制冷剂流量减少，无法充分覆盖蒸发器面积，仅在局部区域膨胀吸热形成低温点。

制冷系统中缺氟引发结霜的机理可从热力学和流体动力学角度深入分析。当系统氟利昂不足时，制冷剂在膨胀阀节流后的压力显著降低。以R22制冷剂为例，其饱和压力在0℃时为0.399MPa，若低压侧压力低于此值，蒸发器表面温度将降至0℃以下。此时流经蒸发器的空气所含水分会在低温金属表面析出并冻结成霜晶。这种现象在家用空调和冰箱中均有体现，但具体表现存在差异：空调缺氟时粗管（回气管）结霜需特定条件，而冰箱冰柜采用R134a等制冷剂时，当饱和压力降至0.193MPa（表压）以下即易出现结霜。

从蒸发过程看，缺氟导致制冷剂流量减少，无法在蒸发器全长范围内充分吸热气化。制冷剂仅在膨胀阀出口附近区域剧烈膨胀，造成该区域温度骤降。此时蒸发器形成"局部过冷-整体过热"的特殊状态：膨胀阀附近因冷媒急剧汽化而结霜，远端却因制冷剂过早完全气化导致回气过热度升高。这种不均匀的热交换会使霜层从膨胀阀端逐渐向回气端延伸，最终可能覆盖整个蒸发器表面。

系统运行参数变化也能印证该机理。实测数据显示，正常工况下蒸发温度应比环境温度低8-12℃，而缺氟系统该温差可能扩大至15℃以上。例如环境温度25℃时，正常蒸发温度约13-17℃，缺氟时可降至10℃以下。这种过低的蒸发温度使得蒸发器表面温度更易达到结霜临界点。制冷剂质量流量不足还会导致系统循环量降低，压缩机吸气比容增大，单位容积制冷量下降，这些都会加剧蒸发器的结霜趋势。

从传热学角度分析，初期形成的霜层会进一步恶化热交换条件。霜层的导热系数仅约0.5W/(m·K)，远低于铜管的401W/(m·K)，相当于在蒸发器表面增加了隔热层。这导致制冷剂需要更低的蒸发温度才能维持换热量，形成"结霜-隔热-更严重结霜"的恶性循环。实验表明，当霜层厚度达2mm时，换热效率可能下降30%以上。

不同制冷设备的结霜特征也有所区别。家用空调在缺氟时通常表现为蒸发器入口端结霜，而冰箱由于蒸发温度更低，可能出现整个蒸发器均匀结霜。商用冷库若使用R404A等制冷剂，缺氟时结霜多始于蒸发器后半段。这些差异主要源于各系统设计压力、蒸发器结构及制冷剂特性的不同。

维修实践中可通过多项指标判断缺氟性结霜：测量低压侧压力低于标准值30%以上；观察膨胀阀出口首先出现"白霜"；检测压缩机工作电流较额定值偏低15%-20%。准确的诊断还需结合温度测量，当蒸发器进出口温差超过8℃时，即可初步判定为制冷剂不足。及时补充适量制冷剂能有效消除结霜现象，恢复系统正常运行。

本题链接：

缺氟结霜制冷系统